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MAR  22  1981 


THE  HYDROSTATIC  SYSTEM  OF  TREES 


BY 

D.  T.  MacDOUGAL 


i 


Published  by  the  Carnegie  Institution  of  Washington 

Washington,  April,  1926 


CARNEGIE  INSTITUTION  OF  WASHINGTON 

Publication  No.  373 


PRESS  OF  GIBSON  BROTHERS,  INC. 


WASHINGTON,  D.  C. 


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CONTENTS. 

Page. 


Conclusions  and  theoretical  conceptions  upon  which  present  work  was  based .  1 

Manometric  measurements  of  suction  and  pressure  in  bores  and  stumps .  6 

Suction  in  cut  ends  of  roots  of  Monterey  pine .  8 

Factors  in  suction  and  pressure  in  roots  of  Pinus .  17 

Suction  at  upper  end  of  small  pine  tree .  18 

Suction  and  pressure  in  outer  layers  of  trunks  of  large  pine  trees .  27 

Nature  of  exudation  pressure  of  the  pine .  42 

Test  for  “root  pressure”  in  pine  trees .  44 

Composition  and  action  of  gases  in  trunks  of  pine  trees .  45 

Suction  and  pressure  in  radial  and  tangential  bores .  48 

Extended  tests  of  bores  and  stumps  of  a  single  pine  tree .  51 

Effects  of  artificial  suction  applied  to  roots  and  stems .  58 

Application  of  suction  to  layers  of  wood  carrying  water-column .  60 

Modifications  of  pressures  induced  by  suction  applied  to  ends  of  stems  and  to  sap¬ 
conducting  layers .  66 

Suction  force  in  trunk  of  Monterey  pine  killed  by  defoliation .  76 

Carbohydrates  in  sap  of  Monterey  pine .  79 

Suction  in  Quercus  agrifolia .  81 

Suction  and  conduction  of  dye  in  small  oak  tree .  89 

Composition  of  gases  in  central  cylinder  of  trunk  of  oak .  92 

Sap  pressures  in  Juglans  major .  93 

Composition  of  internal  gases  of  Juglans .  103 

Conditions  affecting  tension,  suction  and  pressure  in  Juglans .  103 

Suction  and  pressure  in  a  tangential  bore .  108 

Suction  and  pressure  in  a  radial  bore .  109 

Suction  in  short  stub  of  branch .  Ill 

Suction  at  end  of  long  leafy  branch .  112 

Suction  and  pressure  at  terminal  or  distal  end  of  an  excised  root .  113 

Suction  and  pressure  in  a  separated  part  of  the  root .  114 

Discussion .  116 

Summary .  123 


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THE  HYDROSTATIC  SYSTEM  OE  TREES. 

By  D.  T.  MacDOUGAL. 


CONCLUSIONS  AND  THEORETICAL  CONCEPTIONS  UPON 
WHICH  PRESENT  WORK  WAS  BASED. 

It  is  obvious  that  any  definite  knowledge  of  the  “ascent  of  sap”  or 
of  any  of  the  major  movements  of  liquids  in  large  plants  must  rest 
upon  a  comprehension  of  the  hydrostatic  conditions  as  a  whole. 

The  separate  factors  are  doubtless  most  easily  to  be  measured  in 
large  shoots,  such  as  trees,  and  less  advantageously  in  vines.  It  has 
been  made  abundantly  evident,  however,  that  fragmentary  studies 
on  such  separate  phenomena,  as  root-pressure,  “negative”  pressure, 
sap  conduits,  or  any  segregated  translocatory  phenomena  may  not  be 
expected  to  furnish  the  basis  of  any  serious  advance  in  knowledge  of 
the  complex  hydrodynamics  of  trees. 

The  hypotheses  which  have  been  advanced  in  explanation  of  the 
movements  of  sap  beginning  with  the  presentation  of  the  conclusions 
of  Grew  to  the  Royal  Society  of  London  in  May  1671,  and  the  submis¬ 
sion  of  a  manuscript  by  Malphigi  on  the  same  subject  in  December  of 
the  same  year  are  many.1  Actual  advance  since  the  experiments  of 
Stephen  Hales  published  in  1727  has  been  at  the  cost  of  an  enormous 
total  of  labor  and  experiment.  Much  of  the  voluminous  literature 
is  devoted  to  criticism  and  to  the  delimitation  of  the  possibilities. 

The  proposals  of  Dixon  as  to  the  maintenance  of  a  cohesive  mesh- 
work  column  of  water  in  the  wTood,  from  the  roots  to  the  menisci  in  the 
transpiring  walls  of  living  cells  in  the  leaves,  is  to  be  named  as  an  endur¬ 
ing  conception  and  as  a  feature  of  the  hydrodynamics  of  the  plant 
which  has  been  confirmed  by  all  results  in  the  present  paper. 

It  is  unnecessary  to  make  a  comprehensive  discussion  of  the  work  of 
Strasburger  on  the  anatomy,  arrangement  and  action  of  conduits,  or 
to  review  the  w'ork  of  Ewart  in  this  place.  Articles  by  Ursprung  2  and 
by  Renner  3  and  others  are  admirable  examples  of  discussions  of  certain 
phases  of  the  hydrodynamics  of  the  plant. 

It  is  notable  that  no  satisfactory  delineation  has  been  made  of  the 
manner  in  which  the  leaf  products  are  moved  with  adequate  speed  in 
the  required  volume  toward  the  bases  of  stems.  The  present  paper 
includes  results  upon  which  certain  phases  of  sap  pressure  are  explain¬ 
able.  Not  all  “root-pressures”  are  accounted  for,  however. 

1  Grew',  N.  The  anatomy  of  plants.  1682.  See  Preface  and  p.  26,  Book  1,  Malphigi,  Opera 
Omnia.  1687. 

2  Ursprung,  A.  Einige  Resultate  der  neusten  saugkoftstudien.  Flora,  18-19,  566,  1924-5. 

3  Renner,  O.  Die  PorenwTeite  der  Zellhaute  in  ihrer  Beziehung  zum  salftsteigen.  Ber.  d.  deut. 
Bot.  Ges.,  43,  207,  1925. 


1 


2 


HYDROSTATIC  SYSTEM  OF  TREES. 


The  state  of  the  problem  described  is  one  in  which  the  separate 
researches  in  the  field  have  not  been  so  closely  joined  as  to  form  a  good 
foundation  for  general  conclusions.  Results  from  different  types  of 
stems  have  been  unwarrantably  compared.  Manometric  measure¬ 
ments  of  “sap  pressures”  have  been  made  with  no  definite  observation 
of  the  structures  or  tissues  affected  by  the  bores  or  excisions,  so  that  at 
the  present  time  data  as  to  this  topic  constitute  a  hopeless  hodge¬ 
podge.  The  writer  acknowledges  no  obligation  to  arrange  these  in 
order  or  to  correlate  the  figures  with  those  given  on  the  following  pages. 

The  present  approach  to  this  subject  has  been  made  on  the  basis  of 
studies  of  hydration  phenomena  of  dead  and  living  cells  in  which 
changes  in  volume  were  measured  by  the  auxograph;  on  the  nature 
of  the  reversible  variations  in  volume  of  tree-trunks;  on  phenomena  of 
growth  as  recorded  by  the  dendrograph,  and  upon  extensive  experi¬ 
ments  dealing  with  exudation  pressures  and  suction  force  in  vines, 
columnar  cacti,  oaks,  pines  and  walnut  trees.  The  extent  of  this  work 
is  described  in  various  publications  since  1914. 

The  general  conclusions  reached  may  be  profitably  anticipated  to 
some  extent  for  the  purpose  of  presenting  a  unified  conception  of  the 
large  leafy  plant  as  a  hydrostatic  system.  This  was  attempted 
recently  in  a  previous  paper.1  Some  important  modifications  based 
upon  results  in  the  present  paper  are  now  proposed.  The  principal 
advances  concern  the  body  of  gas  in  the  older  wood;  the  capillary  ex¬ 
tension  of  the  water  column  in  this  wood ;  the  strictness  of  conduction 
of  solutions  in  the  outer  layers;  or  more  briefly  stated,  the  localization 
of  mechanical  factors  and  of  the  physiological  action  affecting  move¬ 
ments  of  solutions. 

The  following  features  are  to  be  taken  into  account  in  my  compre¬ 
hensive  study  of  the  hydrostatic  system  of  the  higher  plants. 

(A)  Solutions  enter  the  roots  of  plants  via  the  root-hairs  and  through 
the  endodermis  with  its  turgid  cells  and  heavy  rigid  radial  (transverse 
and  longitudinal)  walls.  The  tangential  walls  are  more  permeable. 
Water  of  the  soil-solutions  is  drawn  through  the  endodermis  whenever 
the  osmotic  value  of  the  elements  internal  to  the  endodermis  is  greater 
than  that  of  the  cortex,  root-hairs  and  soil-solutions,  in  a  manner  but 
little  affected  by  the  superior  turgidity  of  the  endodermal  sheath. 
Ions  of  soil-salts  pass  into  the  root  at  a  rate  and  in  a  manner  determined 
by  their  specific  mobilities,  effects  on  the  colloidal  plasmatic  layers  and 
implied  interferences  or  “antagonistic”  effects. 

Between  the  arrival  of  water,  soil-salts  and  sugars,  in  the  living  cells 
internal  to  the  endodermal  sheath,  and  the  passage  of  the  solution  into 
the  dead  conduits  of  the  roots  communicating  with  the  recently  formed 
wood  is  some  form  of  exudative  or  secretive  action,  not  yet  perfectly 

1  MacDougal,  D.  T.  Absorption  and  exudation  pressures  in  plants.  Proc.  Amer.  Phil.  Soc., 
64,  102-130,  1925. 


MacDOUGAL 


Figure  1 


Internal 

Gases 

PINE 

Co  2,  3+ pet 
O2.  15-f  pet. 

oa  n 

C02.  4+  pet 
02  15  pet 


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MacDOUGAL 


Figure  1 


Internal 

Oases 

PINE 

Co  2,  3-fpct. 
O2.  15-f  pet. 

OA  ft 

C02.  4+  pet. 

O2.  15  pet. 

WALNUT 
C02.  12  pet. 
02*  9  pet. 


Hydrostatic  System  of  the  Tree. 

The  tree  consists  of  an  inner  cylinder 
of  older  wood,  completely  enclosed  in  a 
layer  of  living  cells  extending  from  the 
root  caps  to  the  vegetative  cones  at  the 
tips  of  the  stems  and  its  branches.  The 
living  layer  is  continuous  to  the  lamina. 
The  leaves  are  inserted  through  the  living 
layer  to  connect  with  the  wood  formed  in 
the  previous  year,  or  preceding  years. 
The  older  wood,  D,  includes  atmospheric 
gases  of  a  composition  illustrated,  at 
pressures  varying  from  —0.5  atm.  to 
something  atmospheric  in  the  autumnal 
condition.  The  rays,  C,  are  plates  of 
short  tracheids  and  living  parenchyma¬ 
tous  cells  terminating  in  the  initial  layer 
in  the  cambium  outwardly.  The  par¬ 
enchymatous  cells  of  the  rays  remain 
alive  in  the  older  wood  for  periods 
of  varying  length  in  different  species. 
The  high  proportion  of  CO2  in  the  wood 
may  be  ascribed  to  the  respiratory  activi¬ 
ties  of  these  and  other  living  cells  in  the 
wood.  B,  newly  formed  wood  in  which 
the  upwardly  moving  column  of  sap 
under  tension  is  found.  This  movement 
is  due  to  the  pull  from  the  menisci  in  the 
leaves,  G,  and  to  the  exudation  pres¬ 
sure  when  shown  by  the  roots  at  A... 
E,  growing  point,  F,  petiole  of  leaf. 


THE  COLUMBIA  PLANOORAPH  CO.,  WASHINGTON,  D.  C. 


BASIS  OF  PRESENT  WORK. 


3 


understood  and  not  to  be  passed  lightly.  The  continuous  and  advanc¬ 
ing  zone  of  maturity  in  the  wood  and  conduits  frees  some  material 
from  the  osmotic  mechanism  of  living  cells.  This  material  attracting 
some  water  would  set  up  a  head  of  pressure  which  would  tend  to  force 
solution  up  through  the  stems,  where  it  might  be  measured  as  “root” 
or  exudation  pressure.  In  addition  living  cells,  which  have  a  common 
wall  with  dead  conduits  or  tracheids,  might  show  an  increased  per¬ 
meability  on  this  part  of  their  periphery  which  might  result  in  long- 
continued  excretion  of  water  into  the  conduits.  Such  specialized 
permeability  might,  for  example,  result  from  the  displacement  of 
calcium  in  sectors  of  the  plasmatic  layers  or  membranes  by  potassium 
or  sodium.  It  is  well  known  that  alterations  of  this  kind  in  root- 
hairs  allow  the  passage  or  leakage  of  sugars,  amino-compounds  or 
large  ions  at  a  high  rate. 

This  excretory  action  is  one  in  which  each  living  parenchymatous  cell 
would  pass  through  a  definite  cycle  of  hydration,  accompanied  by 
expansion  followed  by  contraction  and  loss  of  contents  into  the  conduct¬ 
ing  tracts,  followed  by  a  partial  or  total  collapse.  Such  action  has  been 
studied  in  the  thick  cortical  layers  of  the  tree  cacti  where  the  cells 
abutting  on  bores  first  absorb  water  introduced  through  a  manometer 
setting  up  a  measurable  suction.  Later  the  increased  permeability  of 
the  cell  layers  allows  the  osmotic  potential  to  be  expressed  as  exudation 
pressures,  which  must  be  in  every  essential  identical  with  the  pressures 
set  up  in  roots.  Whether  or  not  such  pressures  may  be  shown  by 
stem-bases  and  attached  root-systems  may  be  determined  by  many 
factors  including  such  anatomical  features  as  the  amount  and  character 
of  the  parenchyma  in  the  central  cylinder  of  the  roots. 

(. B )  The  freely  moving  liquids  of  the  stem  move  upwardly  most 
abundantly  in  the  recently  formed  wood  layers  to  which  the  leaves  are 
attached  terminally.  In  the  Monterey  pine  the  leaves  are  retained  a 
second  or  third  year,  and  are  formed  directly  on  the  axes  of  nodes  of 
the  terminal.  The  sap  stream  in  such  cases  follows  the  second,  third 
and  fourth  layers  on  the  older  parts  of  the  stem,  and  the  first,  second 
and  perhaps  the  third  in  the  terminal  parts.  The  layers  may  not  be 
so  strictly  defined  in  the  oak,  walnut  or  other  trees  examined.  The 
presence  of  extensively  connected  tracheae  in  the  wood  modifies  the 
pattern  somewhat. 

In  any  case  solutions  may  move  radially  chiefly  through  the  rays, 
the  tracheids  of  which  are  not  to  be  taken  as  emptied  of  colloidal  con¬ 
tents  so  soon  as  the  longitudinal  elements.  Circumferential  or  tangen¬ 
tial  movement  is  also  slow,  as  will  be  shown  by  the  results  of  pumping 
sap  from  bores  in  the  ends  of  trunks. 

(C)  The  cambium  of  a  tree  constitutes  a  continuous  layer,  several 
cells  in  thickness  over  the  entire  plant,  and  is  pierced  only  by  the 
leaves.  These  organs  interpose  living  cells  between  the  atmosphere 


4 


HYDROSTATIC  SYSTEM  OF  TREES. 


and  the  wood,  although  connection  prevails  between  the  loosely 
arranged  parenchyma  of  the  leaves  and  the  cortex  of  stems.  The 
cortex  communicates  by  lenticels  and  rifts  directly  with  the  atmosphere. 
Samples  of  the  gases  taken  by  suction  from  an  entire  cut  end  of  a 
stem  may  therefore  be  expected  to  show  a  composition  not  widely 
different  from  that  of  the  air. 

The  recently  formed  wood  carrying  the  column  of  sap,  in  which  the 
elements  of  the  rays  are  alive  or  present  themselves  as  colloidal 
masses,  forms  a  second  enclosure  of  the  woody  column  of  a  tree,  through 
which  diffusion  of  gases  or  liquids  may  take  place  but  slowly.  That 
such  enclosure  is  practical  and  effective  is  plainly  evident  from  the 
results  of  the  analyses  of  the  gases  taken  from  the  central  cylinder  of 
the  oak,  pine  and  walnut,  which  in  the  autumnal  condition  are  in  pro¬ 
portions  widely  different  from  those  of  the  surrounding  atmosphere. 

An  active  respiration  in  the  inner  living  cells  or  rays  would  cause  an 
increase  in  the  proportion  of  carbon  dioxide,  and  would  tend  to  increase 
the  amount  of  diffusion  from  the  central  cylinder,  with  consequent 
lessening  of  pressure,  a  matter  to  which  attention  was  called  in  190 1.1 
An  increased  proportion  of  carbon  dioxide  in  the  wood  would  also 
cause  a  higher  suction  pressure  to  show  in  manometers  attached  to 
bores  or  stems  by  tubes  filled  with  water. 

Both  composition  of  the  gases  in  the  woody  cylinder  and  the  state 
of  pressure  may  vary  widely.  No  recent  contributions  to  this  subject 
have  been  made,  but  comprehensive  recapitulations  are  given  by 
Pfeffer,2  and  by  Palladin  and  Livingston.3 

The  security  with  which  the  enclosed  air-body  is  held  and  its  varying 
composition  render  it  of  great  importance  to  the  hydrostatic  system, 
in  which  it  performs  a  mechanical  function  comparable  to  that  of  the 
air-chamber  in  force  and  suction  pumps  which  the  plant  constitutes. 
Early  in  the  course  of  the  experiments  described  in  the  present  paper  it 
was  found  that  in  all  manometric  work  the  nature  of  the  connection 
of  the  bore  or  of  the  leading  tube  of  the  pressure  gage  was  of  great 
importance.  Gages  inserted  in  the  cortex,  in  the  water-conducting 
layers,  or  which  connected  with  all  three  naturally  gave  diversified 
results.  The  attempt  has  been  made  to  carry  out  more  definite  tests 
and  to  correlate  results  obtained  from  different  parts  of  the  plant 
machine. 

(D)  Positive  or  exudation  pressures  have  been  observed  in  stems  by 
instruments  attached  to  bores  and  to  stumps  for  extended  periods. 
Such  action  may  be  due  to  hydration  phenomena  as  described  in  (A). 
Liquids  may  be  forced  to  carrying  heights  in  stems  by  such  action. 
Transpiration  of  water  from  the  minute  menisci  in  the  walls  of  tran- 

1  MacDougal,  D.  T.  Practical  text-book  of  plant  physiology.  Page  189,  1901. 

2  Movements  and  pressure  of  internal  gases,  in  Physiology  of  Plants.  Trans,  by  A.  J.  Ewart, 
vol.  1,  199-206,  1900. 

3  Movements  of  gases,  in  Palladin' s  Plant  Physiology.  Ed.  by  B.  E.  Livingston,  118-121, 
1918. 


BASIS  OF  PRESENT  WORK. 


5 


spiring  leaf-cells  sets  up  a  tension  in  the  column  of  water  which  extends 
downward  in  the  trunk,  and  it  is  this  pull  which  constitutes  the  prin¬ 
cipal  lifting  force  in  the  ascent  of  sap.  The  increased  loss  of  water  and 
the  attenuation  of  the  column  is  followed  by  a  shrinkage  or  contraction 
of  the  cambium  and  living  layers  of  cells  and  of  the  outer  layers  of 
wood  in  a  manner  characteristic  of  the  species  as  shown  by  the  den- 
drographic  record.  Concurrent  variations  in  pressure  are  shown  by 
water-filled  gages  connecting  with  the  sap-filled  layers,  the  central 
cylinder,  and  with  the  cortex,  but  the  correlations  between  the  varia¬ 
tions  of  pressure  measured  by  the  manometer  and  of  variations  in 
diameter  have  been  made  for  two  or  three  phases  only. 

(E)  Various  roles  have  been  ascribed  to  living  cells  in  attempted 
explanations  of  the  mechanism  of  movement  of  solutions  in  stems. 
The  cambium  external  to  the  wood  has  not  been  taken  as  an  active 
factor  beyond  its  action  in  the  production  of  new  elements  and  in  the 
maintenance  of  a  complete  layer  of  cells,  which  effectually  stops  capil¬ 
lary  movements  radially  and  is  only  slowly  permeable  to  the  gases  of 
the  central  cylinder. 

The  tracheids  of  the  conifers  and  also  the  tracheae  of  dicotyledonous 
trees  are  in  intimate  connection  with  the  living  cells  of  the  rays  and 
with  the  parenchyma  which  sheathes  the  vessels.  The  sap  stream  is, 
therefore,  moving  upward  in  conduits  which  may  be  elongated  tubes 
or  wood  cells  intercommunicating  by  minute  perforations,  but  which 
are  in  contact  with  the  sheets  or  plates  of  short  tracheids  and  living 
parenchyma  of  the  medullary  rays. 

The  exchanges  between  the  two  kinds  of  elements  may  be  very  com¬ 
plicated.  Ions  of  salts  coming  from  the  soil  would  pass  into  the  rays 
and  other  external  elements,  as  into  the  roots,  in  a  manner  determined 
by  their  own  mobility  and  specific  effect  on  the  cell  colloids.  Such 
effects  might  include  marked  changes  in  permeability  as  a  result  of 
which  material  of  almost  any  kind  might  be  exchanged  between  the 
wood  and  living  elements.  If  these  changes  were  such  as  cause  a  con¬ 
traction  of  the  living  cells,  liquid  would  be  forced  into  the  wood  and 
might  show  as  root-pressure  in  a  gage  attached  to  a  bore  in  the  wood. 
On  the  other  hand,  the  osmotic  balance  might  be  such  that  water  would 
be  drawn  from  solutions  of  low  concentration  in  the  wood  or  vessels 
and  carried  across  to  the  cambium.  However,  this  interplay  may  be 
balanced,  and  it  is  clear  that  the  total  thickness  of  the  young  wood  is 
lessened  at  the  time  of  greatest  water-loss  from  the  leaves.  It  seems 
obvious  that  the  tension  set  up  in  the  water-column  by  the  pull  from 
the  leaves  would  result  in  contraction  at  a  time  when  usually,  by  reason 
of  the  higher  temperatures,  the  suction  force  of  the  living  cells  in  the 
rays  and  sheaths  is  greatest.  Whether  or  not  such  intake  of  water 
could  proceed  to  an  extent  that  a  condition  of  high  hydration  was 
reached  in  which  water  would  be  lost  to  the  wood  cells  is  a  matter  vet 

V 

to  be  determined.  If  affirmed  it  would  imply  a  conjunction  of  the  living 


6 


HYDROSTATIC  SYSTEM  OF  TREES. 


cells  of  the  stem  with  those  of  the  root  in  forcing  water  upward.  The 
results  presented  do  not  bear  directly  on  this  possibility. 

(F)  Fragmentary  results  as  to  the  hydrogen  ion  concentration  yield 
the  conception  that  the  cambium  is  not  far  from  neutral,  and  that  the 
pH  increases  inward  in  the  new  wood  and  outward  toward  the  bark. 
One  of  the  major  problems  concerns  the  mechanism  of  translocation  of 
leaf-products  downward  through  long  stems.  Conduction  through 
the  phloem  has  long  been  held  as  a  tentative  proposal,  but  the  amount 
of  material  moved  is  such  that  many  difficulties  are  obvious.  The 
liquid  in  older  wood  is  under  tension  and  is  constantly  pulled  toward 
the  leaves.  The  wood  of  the  current  year  is  under  such  tension  only 
indirectly.  If  it  were  allowable  to  assume  that  the  older  wood  com¬ 
municated  more  freely  at  the  base  of  the  stem,  the  upward  pull  in  the 
sap  current  would  operate  to  draw  solutions  down  through  the  newer 
wood.  Such  a  proposal  is  purely  hypothetical,  but  the  arrangement 
is  a  possible  one  and  would  be  an  efficient  means  of  transporting 
material  downward  through  large  stems.  Something  of  this  kind 
has  been  suggested  by  Dixon. 

MANOMETRIC  MEASUREMENTS  OF  SUCTION  AND  PRESSURE 

IN  BORES  AND  STUMPS. 

The  conception  of  the  hydrostatic  system  of  the  tree  rests  upon  the 
results  of  observations  on  the  daily  reversible  variations  in  trunks,  the 
rate  and  path  of  solutions,  structures,  stomatal  action  and  upon  ex¬ 
tended  use  of  manometers  on  trunks  of  Pinus  radiata ,  Quercus  agri- 
folia,  Juglans  major,  Sequoia  sempervirens,  Carnegiea  gigantea  and 
other  plants,  following  on  my  extensive  studies  of  the  variation  in 
volume  of  living  cells  in  different  stages  of  hydration. 

The  use  of  manometers  to  determine  the  state  of  pressure  of  the 
gases  and  liquids  in  plant  stems  has  been  practiced  since  the  time  of 
Hales  (1727).  The  actual  connections  with  the  hydrostatic  system,  a 
matter  of  the  greatest  importance,  was  established  in  very  few  experi¬ 
ments.  It  is  clear  that,  when  a  stump  of  a  branch,  stem,  or  root  was 
sheathed  in  a  rubber  tube  which  established  connection  with  a  man¬ 
ometer,  the  variations  recorded  would  be  very  complex,  including  the 
action  of  the  central  air-body,  the  conducting  tracts  and  the  cortex. 
The  first  does  not  communicate  with  the  atmosphere  in  the  intact 
shoot,  and  the  cortex  generally  does  so  freely  through  the  lenticels. 
In  some  cases  the  attachment  of  the  rubber  tube  to  a  stump  would 
result  in  a  compression  of  the  cortex  which  would  close  it  for  longi¬ 
tudinal  conduction  of  air  into  the  manometer.  This  can  not  be 
assumed  in  any  consideration  of  previous  results. 

A  second  source  of  error  lies  in  the  entrance  of  air  into  the  man¬ 
ometer  system  from  the  wood.  The  capillary  entrance  of  water  from 
the  manometer  generally  results  in  the  displacement  of  some  gases 
which  collect  in  the  manometer;  also,  as  soon  as  suction  is  set  up  an 
increased  emission  of  gas  results  in  some  cases.  A  type  of  man- 


MANOMETRIC  MEASUREMENTS  IN  BORES  AND  STUMPS. 


7 


ometer  was  designed  so  that  accumulated  air  could  be  eliminated 
(figs.  2  and  3).  It  is  to  be  noted  in  this  connection 
that  when  a  bore  is  made  into  the  interior  air-filled 
cylinder  of  a  trunk  and  filled  with  water  that  capillary 
action  results,  and  that  some  interpretation  of  the 
measurements  is  necessary.  Previous  results  having 
yielded  information  by  which  some  of  the  main 
features  of  the  gas 
and  water  systems 
illustrated  in  figure 
1  were  discernible, 
plans  were  made  for 
connecting  manom¬ 
eters  with  various 
parts  of  this  system 
in  trunks,  roots  and 
branches  of  the 
Monterey  pine  (Pi- 
nus  radiata),  trunks 
of  oak  ( Quercus  agri- 
folia),  and  in  trunks, 
branches  and  roots 
of  the  walnut  (Jug- 
lans  major)  at  Car¬ 
mel,  California,  in 
the  growing  season 
of  1925.  Installa¬ 
tion  of  a  suite  of 
instruments  was  be¬ 
gun  in  April  and 
observations  were 
continued  for  7 
months.  In  order 
to  effect  the  complete  correlation  and  to  procure  uniformity  in  manipu¬ 
lation,  nearly  all  readings  and  all  adjustments  of  apparatuses  in  meas¬ 
urement  of  suction  and  pressure  were  made  by  the  author,  and  as  may 
be  seen  no  period  of  more  than  a  day  or  two  was  allowed  to  pass  with¬ 
out  some  observations  being  made.  Meteorological  records  are  kept 
as  part  of  the  routine  of  the  Coastal  Laboratory,  and  some  references 
are  made  to  them.  It  seemed  advisable,  however,  to  note  conditions 
of  weather  in  connection  with  every  series  of  measurements.  Temper¬ 
atures  of  the  newly  formed  wood  in  the  trunk  of  the  walnut  tree  were 
taken  by  mercurial  thermometer  with  a  slender  bulb  fixed  tightly  in 
a  cavity  made  for  it.  (See  fig.  19.)  Parallel  conditions  may  be 
assumed  in  the  other  trees. 

The  results  of  the  observations  are  given  on  the  following  pages, 
those  on  roots  of  the  pine  being  taken  up  first. 


Fig.  2. — Manometer  with  closed  arm  suitable  for  measuring 
amount  of  pressure  which  may  be  set  up,  accompanying  an 
exudation  of  1  to  3  ml.  of  sap.  Stopcock  and  filling  funnel 
are  provided  to  release  air  drawn  from  tree  and  for  renewal 
of  watery  solution  used. 

Fig.  3. — Manometer  with  open  end,  stopcock  and  filling  funnel 
for  readjustment.  The  open  arm  has  a  bore  about  2  mm. 
in  diameter.  This  type  of  instrument  was  used  extensively 
for  recording  daily  variations,  being  especially  useful  when 
changes  from  less  than  atmospheric  to  more  than  atmos¬ 
pheric  pressures,  and  vice  versa,  were  encountered. 


8 


HYDROSTATIC  SYSTEM  OF  TREES. 


SUCTION  IN  CUT  ENDS  OF  ROOTS  OF  MONTEREY  PINE. 

The  terminal  end  of  a  root  cut  60  cm.  from  the  base  of  a  small  tree 
(. Pinus  radiata,  No.  XI)  was  fitted  with  a  manometer  with  a  closed 
end  at  first,  as  illustrated  in  figure  3,  which  was  later  replaced  by  one  as 
in  figure  4. 

The  tree  had  grown  up  slenderly  in  shade,  with  a  diameter  of  only 
6  cm.  near  the  base,  although  the  stem  was  over  7  meters  in  height. 
The  branches  were  few  and  small,  so  that  the  transpiratory  draft  on  the 
root  system  was  less  than  the  average.  The  first  fitting  of  the  instru¬ 
ment  was  made  on  July  6  and  proved  to  be  de¬ 
fective,  probably  by  leakage  through  the  cortical 
layers.  The  record  is  given  in  Table  1,  in  which 
suction  is  denoted  by  —  sign  before  the  figure 
denoting  the  difference  between  the  mercury 
columns  in  the  two  arms  of  the  U  tube  of  the 
manometer.  The  actual  amount  is  always 
slightly  greater  by  the  weight  of  the  water  in  the 
_  .  arm  connected  with  the  bore. 


'J 


Fig.  4. — Manometer  with  vertical  arm,  B,  standing  in  dish  of  mercury  attached  to  terminal 
end  of  cut  root,  A,  of  small  pine  tree.  Stopcock  and  filling  funnel  serve  to  release 
gases  drawn  out  of  root  and  to  renew  solutions.  Attached  to  Monterey  pine  No.  XI. 


SUCTION  IN  CUT  ENDS  OF  ROOTS  OF  MONTEREY  PINE. 


9 


Table  1. 


Date. 

Time. 

Suction 

or 

pressure 

in 

mm.  Hg. 

Remarks. 

1925 

July  6 

8h30m  a.  m. 

Instrument  fitted. 

9  a.  m. 

-  5 

Clear. 

10  a.  m. 

-  5 

Do. 

11  a.  m. 

-  8 

Do. 

6  30  p.  m. 

-  6 

Overcast. 

July  7 

7  a.  m. 

-  6 

Do. 

9  a.  m. 

-  6 

Overcast. 

2  p.  m. 

-  6 

Clear. 

July  8 

7  30  a.  m. 

-  6 

Overcast. 

9  30  a.  m. 

-  6 

Clearing. 

2  p.  m. 

-  7 

Clear. 

4  p.  m. 

-  6 

Overcast. 

July  11 

7  30  a.  m. 

-  6 

Clear. 

11  a.  m. 

-  6 

2  30  p.  m. 

-  6 

Taken  down;  surface  of  root  dry  and  a  slice  was  re- 

• 

moved  before  instrument  was  refitted. 

3  p.  m. 

-  18 

Clear  and  warm. 

4  30  p.  m. 

-  63 

Do. 

July  12 

8  a.  m. 

-104 

Do. 

10  30  a.  m. 

-117 

Do. 

July  13 

7  30  a.  m. 

-108 

Air  released;  set  to  0  with  stopcock  open. 

9  30  a.  m. 

•  •••••••• 

Stopcock  closed. 

12  m 

-  66 

3  30  p.  m. 

-132 

Clear. 

July  14 

7  30  a.  m. 

-115 

Air  released;  set  to  0. 

11  15 '  a.  m. 

-  53 

2  15  p.  m. 

-  92 

Alternating  sunshine  and  clouds. 

July  15 

7  30  a.  m. 

-135 

Foggy;  air  released;  set  at  0. 

9  30  a.  m. 

-  10 

Clear. 

1  30  p.  m. 

-  66 

Do. 

July  16 

7  a.  m. 

-162 

Do. 

11  a.  m. 

-168 

Clear. 

3  30  p.  m. 

-162 

Do. 

July  17 

7  a.  m. 

-126 

Air  released ;  set  to  0. 

3  15  p.  m. 

•  •••••••• 

Stopcock  closed. 

July  18 

7  a.  m. 

42 

Clouds. 

11  30  a.  m. 

-  66 

Do. 

4  p.  m. 

-  78 

Do. 

July  19 

7  40  a.  m. 

-  35 

Air  out;  set  to  0. 

10  a.  m. 

-  14 

3  p.  m. 

-  26 

Clouds. 

July  20 

7  a.  m. 

-  10 

Air  released.  Taken  down,  a  few  mm.  sliced  from  end; 

reset  at  0. 

11  30  a.  m. 

-  3 

Clouds. 

3  30  p.  m. 

-  3 

Clear. 

July  21 

7  a.  m. 

-  2 

Overcast. 

11  a.  m. 

•  •••••••• 

Do. 

4  p.  m. 

•  •••••••• 

Clouds  and  sun. 

July  26 

7  30  a.  m. 

-  10 

Fog.  Had  been  inactive  since  the  21st. 

3  p.  m. 

-  8 

Overcast. 

July  27 

7  30  a.  m. 

-  12 

Do. 

11  30  a.  m. 

-  12 

Do. 

2  30  p.  m. 

-  13 

Do. 

July  28 

7  a.  m. 

-  19 

Do. 

11  a.  m. 

-  18 

Do. 

2  p.  m. 

-  20 

Clear. 

July  29 

7  40  a.  m. 

-  24 

Overcast. 

July  30 

8  a.  m. 

-  29 

Dripping  fog. 

4  p.  m. 

-  27 

Overcast. 

10 


HYDROSTATIC  SYSTEM  OF  TREES 


Table  1 — Continued. 


Date. 

Time. 

Suction 

or 

pressure 

in 

mm.  Hg. 

Remarks. 

1925 

July  31 

8h  m  a.  m. 

-  33 

Overcast. 

11  30  a.  m. 

-  35 

Sun  coming  out. 

Aug.  2 

3  45  p.  m. 

-  48 

Clear. 

Aug.  3 

7  30  a.  m. 

-  51 

Overcast. 

11  30  a.  m. 

-  50 

Clear. 

3  40  p.  m. 

-  51 

Do. 

Aug.  4 

8  a.  m. 

-  55 

Overcast. 

2  30  p.  m. 

-  56 

Clear. 

Aug.  5 

9  a.  m. 

-  62 

Fog. 

Aug.  6 

2  30  p.  m. 

-  66 

Clear. 

Aug.  7 

9  a.  m. 

-  69 

Fog. 

4  p.  m. 

-  72 

Clear. 

Aug.  8 

8  a.  m. 

-  76 

Fog. 

4  p.  m. 

-  75 

Warm. 

Aug.  9 

8  30  a.  m. 

-  82 

Overcast. 

7  p.  m. 

-  81 

Do. 

Aug.  10 

8  a.  m. 

-  84 

Do. 

11  a.  m. 

-  83 

Clear. 

4  p.  m. 

-  86 

Do. 

Aug.  11 

8  a.  m. 

-  90 

Do. 

11  30  a.  m. 

-  86 

Do. 

7  30  p.  m. 

-  92 

Do. 

Aug.  12 

7  30  a.  m. 

-  96 

Do. 

11  30  a.  m. 

-  99 

Do. 

4  15  p.  m. 

-  96 

Do. 

Aug.  13 

7  30  a.  m. 

-101 

Overcast. 

11  30  a.  m. 

-  98 

Do. 

7  p.  m. 

-102 

Sun  in  afternoon. 

Aug.  14 

5  45  a.  m. 

-108 

Overcast. 

8  45  a.  m. 

-105 

Clearing. 

Aug.  15 

11  a.  m. 

-110 

Overcast. 

Aug.  16 

7  30  a.  m. 

-118 

Do. 

4  p.  m. 

-117 

Do. 

Aug.  17 

7  30  a.  m. 

-120 

Do. 

11  30  a.  m. 

-120 

Clear  at  9h30™. 

4  30  p.  m. 

-123 

Clear. 

Aug.  18 

7  30  a.  m. 

-126 

Do. 

11  a.  m. 

-124 

Do. 

4  p.  m. 

-126 

Do. 

Aug.  19 

7  a.  m. 

-133 

Clear  and  sharp. 

11  45  a.  m. 

-132 

Clear  and  warm. 

4  15  p.  m. 

-134 

Do. 

Aug.  20 

7  30  a.  m. 

-134 

Overcast  and  cool. 

11  30  a.  m. 

-134 

Warm  and  sunny. 

Aug.  21 

3  30  p.  m. 

-144 

Do. 

Aug.  22 

8  a.  m. 

-147 

Do. 

11  30  a.  m. 

-145 

Do. 

5  p.  m. 

-147 

Do. 

Aug.  23 

8  a.  m. 

-152 

Misting. 

11  a.  m. 

-152 

Clearing. 

4  30  p.  m. 

-153 

Clear. 

Aug.  24 

7  30  a.  m. 

-156 

Do. 

11  30  a.  m. 

-153 

Do. 

4  p.  m. 

-153 

Do. 

Aug.  25 

7  30  a.  m. 

-160 

Do. 

11  30  a.  m. 

-153 

Do. 

4  p.  m. 

-162 

Do. 

SUCTION  IN  CUT  ENDS  OF  ROOTS  OF  MONTEREY  PINE. 


11 


Table  1 — Continued. 


Date. 

Time. 

Suction 

or 

pressure 

in 

mm.  Hg. 

Remarks. 

1925 

Aug.  26 

8h  m 

a.  m. 

-164 

Overcast. 

11  30 

a.  m. 

-162 

Beginning  to  clear. 

7 

p.  m. 

-165 

Overcast. 

Aug.  27 

6 

a.  m. 

-168 

Do. 

7 

a.  m. 

-169 

8 

a.  m. 

-168 

Clear. 

9 

a.  m. 

-165 

Clouds. 

10 

a.  m. 

-163 

Clear. 

11 

a.  m. 

-162 

12 

m. 

-165 

Clouds. 

2 

p.  m. 

-168 

Overcast. 

3 

p.  m. 

-169 

Do. 

4 

p.  m. 

-169 

Do. 

5 

p.  m. 

-169 

Do. 

8 

p.  m. 

-170 

Clear. 

11 

p.  m. 

-174 

Do. 

Aug.  28 

3 

a.  m. 

-171 

Overcast. 

4 

a.  m. 

-171 

Do. 

6 

a.  m. 

-171 

Do. 

8 

a.  m. 

-171 

Clearing. 

9 

a.  m. 

-171 

Clear. 

10 

a.  m. 

-169 

Clouds  forming. 

Aug.  28 

11 

a.  m. 

-170 

Do. 

2 

p.  m. 

-171 

Clear. 

4 

p.  m. 

-168 

Do. 

7 

p.  m. 

-173 

Clouds. 

9 

p.  m. 

-174 

Do. 

Aug.  29 

3 

a.  m. 

-175 

Overcast. 

4 

a.  m. 

-175 

Do. 

6 

a.  m. 

-175 

Do. 

8 

a.  m. 

-175 

Do. 

Aug.  30 

9 

a.  m. 

-176 

Fog  and  dew. 

12 

m. 

-171 

Clear. 

6 

p.  m. 

-154 

Do. 

Aug.  31 

9 

a.  m. 

-157 

Do. 

4 

p.  m. 

-156 

Do. 

Sept.  1 

7 

a.  m. 

-159 

Rain  clouds. 

12 

m. 

-153 

Clear. 

7 

p.  m. 

-158 

Do. 

Sept.  2 

7 

a.  m. 

-162 

11 

a.  m. 

-155 

Clear. 

Sept.  5 

11 

a.  m. 

-152 

Do. 

6  30 

p.  m. 

-166 

Do. 

Sept.  6 

8  30 

a.  m. 

-167 

Clearing  after  shower. 

6 

p.  m. 

-168 

Clouds. 

Sept.  7 

7  30 

a.  m. 

-168 

Clear  after  shower. 

11  15 

a.  m. 

-165 

Do. 

• 

4  30 

p.  m. 

-170 

Do. 

Sept.  8 

7  30 

a.  m. 

-171 

Do. 

11  30 

a.  m. 

-163 

Clear. 

4 

p.  m. 

-170 

Do. 

Sept.  9 

8 

a.  m. 

-173 

Cloudy  since  early  morning. 

11  30 

a.  m. 

-168 

Clear. 

Sept.  10 

7  30 

a.  m. 

-173 

Cloudy. 

Sept.  13 

8 

a.  m. 

-176 

Clearing. 

6 

p.  m. 

-176 

Clear. 

Sept.  14 

7  15 

a.  m. 

-178 

Do. 

11  30 

a.  m. 

-173 

Do. 

4 

p.  m. 

-176 

Do. 

12 


HYDROSTATIC  SYSTEM  OF  TREES 


Table  1 — Continued. 


Date. 

Time. 

Suction 

or 

pressure 

in 

mm.  Hg. 

Remarks. 

1925 

Sept.  15 

7h  15m  a.  m. 

-178 

Clear. 

3  30  p.  m. 

-176 

Do. 

Sept.  16 

7  30  a.  m. 

-180 

Clear,  some  clouds. 

Sept.  18 

7  a.  m. 

-183 

Rain  on  17th.  Clouds. 

Sept.  20 

9  a.  m. 

-181 

Clear  and  cool. 

Sept.  21 

7  30  a.  m. 

-185 

Do. 

11  30  a.  m. 

-176 

Clear. 

4  p.  m. 

-183 

Clear  and  cool. 

Sept.  22 

7  30  a.  m. 

-184 

Clear. 

11  30  a.  m. 

-178 

Do. 

5  30  p.  m. 

-185 

Cloudy  since  5  p.  m. 

Sept.  23 

8  a.  m. 

-187 

Cloudy. 

12  m. 

-183 

Clear  after  9  a.  m. 

4  p.  m. 

-185 

Cloudy. 

Sept.  24 

7  15  a.  m. 

-187 

Overcast. 

11  30  a.  m. 

-186 

Clearing. 

4  p.  m. 

-186 

Clouds. 

Sept.  25 

8  a.  m. 

-187 

Clear. 

5  p.  m. 

-187 

Do. 

Sept.  26 

7  15  a.  m. 

-188 

Do. 

11  45  a.  m. 

-180 

Do. 

4  p.  m. 

-185 

Do. 

Sept.  28 

7  30  a.  m. 

-187 

Some  clouds. 

Sept.  29 

9  45  a.  m. 

-190 

Clear. 

Oct.  4 

9  a.  m. 

-187 

Do. 

4  p.  m. 

-187 

Do. 

Oct.  5 

7  30  a.  m. 

-188 

Do. 

2  30  p.  m. 

-185 

Clouds. 

Oct.  6 

7  30  a.  m. 

-188 

Clear. 

5  p.  m. 

-185 

Oct.  7 

7  45  a.  m. 

-187 

Clear. 

12  m. 

-181 

Do. 

3  p.  m. 

-183 

Do. 

6  30  p.  m. 

-185 

Do. 

Oct.  8 

7  30  a.  m. 

-187 

Do. 

4  p.  m. 

-182 

Do. 

Oct.  9 

7  30  a.  m. 

-185 

Cloudy. 

3  30  p.  m. 

-182 

Do. 

Oct.  10 

8  a.  m. 

-182 

Cloudy. 

12  m. 

-182 

Overcast. 

4  p.  m. 

-183 

Do. 

Oct.  12 

8  a.  m. 

-188 

Cloudy;  raining  since  noon  of  11th. 

4  p.  m. 

-183 

Clouds  and  sun. 

Oct.  13 

8  a.  m. 

-186 

Clear  and  cold. 

2  p.  m. 

-182 

Do. 

Oct.  14 

8  a.  m. 

-186 

Do. 

Oct.  16 

9  a.  m. 

-175 

Cloudy. 

4  p.  m. 

-173 

Do. 

Oct.  17 

8  a.  m. 

-173 

Do. 

Oct.  18 

8  a.  m. 

-172 

Clear. 

Oct.  19 

8  a.  m. 

-168 

Do. 

9  a.  m. 

......... 

Reset  at  —194;  small  air  bubble  out. 

4  p.  m. 

-150 

Clear. 

Oct.  20 

7  30  a.  m. 

-143 

Do. 

2  p.  m. 

-145 

Do. 

Oct.  21 

8  a.  m. 

-126 

Do. 

Oct.  22 

4  p.  m. 

-140 

Clear;  reset  at  —172. 

Oct.  23 

7  a.  m. 

. 

Down.1 

1  Instrument  taken  down,  cleaned  and  refitted.  The  part  of  the  root  enclosed  in  the  sheathing 
tube  was  dead,  both  as  to  cortex  and  cambium.  A  slice  was  taken  from  the  end. 


SUCTION  IN  CUT  ENDS  OF  ROOTS  OF  MONTEREY  PINE 


13 


Table  1 — Continued. 


Date. 

Time. 

Suction 

or 

pressure 

in 

mm.  Hg. 

Remarks. 

1925 

Oct.  23 

9h  m  a.  m. 

-160 

Reset  at  this  point  after  re-fitting. 

11  a.  m. 

-156 

Clear  and  warm. 

Oct.  24 

7  a.  m. 

-157 

Clear. 

12  m. 

-155 

Do. 

7  p.  m. 

-156 

Do. 

Oct.  25 

8  a.  m. 

-157 

Do. 

Oct.  26 

7  30  a.  m. 

-122 

Do. 

Oct.  27 

8  a.  m. 

-  90 

Overcast. 

4  p.  m. 

-  85 

Clear. 

Oct.  28 

7  30  a.  m. 

-  87 

Overcast. 

4  p.  m. 

-  88 

Do. 

Oct.  29 

2  p.  m. 

-  90 

Clear. 

Oct.  30 

7  30  a.  m. 

-  93 

Overcast. 

Oct.  31 

8  a.  m. 

-  96 

Do. 

Nov.  1 

10  30  a.  m. 

-  96 

Do. 

Nov.  2 

8  a.  m. 

-  98 

Showers. 

Nov.  3 

9  a.  m. 

-100 

Clearing. 

Nov.  4 

8  a.  m. 

-102 

Do. 

4  p.  m. 

-103 

Clear. 

Nov.  5 

8  a.  m. 

-105 

Do. 

4  p.  m. 

-103 

Do. 

Nov.  6 

8  a.  m. 

-105 

Do. 

3  p.  m. 

-105 

Do. 

Nov.  7 

8  a.  m. 

-107 

Do. 

Nov.  8 

10  a.  m. 

-108 

Do. 

Nov.  9 

8  a.  m. 

-110 

Do. 

3  p.  m. 

-109 

Cloudy. 

Nov.  10 

4  p.  m. 

-112 

Do. 

Nov.  11 

7  30  a.  m. 

-112 

Raining. 

4  p.  m. 

-112 

Do. 

Nov.  12 

8  a.  m. 

-114 

Cloudy. 

4  p.  m. 

-121 

Raining. 

Nov.  13 

7  30  a.  m. 

-115 

Clear. 

Nov.  14 

7  30  a.  m. 

-116 

Do. 

4  p.  m. 

-116 

Do. 

Nov.  15 

8  a.  m. 

-116 

Clear. 

1  30  p.  m. 

-120 

Do. 

4  p.  m. 

-118 

Cloudy. 

Nov.  16 

8  a.  m. 

-120 

Drizzle. 

Nov.  17 

7  30  a.  m. 

-122 

Clear. 

Nov.  18 

7  30  a.  m. 

-123 

Do. 

11  30  a.  m. 

-122 

Do. 

2  p.  m. 

-122 

Do. 

7  p.  m. 

-124 

Do. 

Nov.  19 

7  30  a.  m. 

-124 

Do. 

Nov.  20 

8  a.  m. 

-125 

Do. 

11  30  a.  m. 

-125 

Do. 

2  p.  m. 

-125 

Do. 

4  30  p.  m. 

-126 

Do. 

Nov.  21 

8  a.  m. 

-129 

Overcast. 

12  m. 

-127 

Slightly  overcast. 

4  p.  m. 

-128 

Overcast. 

Nov.  22 

8  a.  m. 

-132 

Clear. 

Nov.  23 

7  30  a.  m. 

-132 

Overcast. 

Nov.  24 

7  30  a.  m. 

-137 

Do. 

2  p.  m. 

-136 

Clear. 

Nov.  25 

7  a.  m. 

-139 

Do. 

2  p.  m. 

-138 

Hazy. 

Nov.  26 

12  m. 

-139 

Do. 

Nov.  27 

8  a.  m. 

-142 

Clear. 

Nov.  28 

8  a.  m. 

-145 

Do. 

14 


HYDROSTATIC  SYSTEM  OF  TREES. 


The  root  of  a  pine  tree  ( Pinus  radiata,  No.  XII),  14  meters  in 
height  and  25  cm.  in  diameter  at  the  base,  was  exposed  for  a  length  of 
2  meters,  beginning  at  a  distance  of  2  meters  from  the  base  of  the  tree. 
The  root  was  cut  at  a  distance  of  2.5  meters  from  the  base  of  the  tree 
where  it  had  a  diameter  of  about  12  mm.  A  manometer  was  attached 


Fig.  5. — Terminal  end  of  root  of  Monterey  pine  No.  XII  with  U  manometer  with  open  end, 
showing  suction  equivalent  to  about  100  mm.  Hg.  Portion  of  separated  root  was  removed 
and  similar  instrument  attached  to  stump  (See  p.  15).  B,  point  at  which  a  second  man¬ 
ometer  was  attached  later. 


to  the  terminus  of  the  root  as  shown  in  figure  5.  A  length  of  50  cm. 
was  cut  from  the  separated  part  or  stump  and  a  similar  manometer 
attached  at  B.  The  leading  tubes  of  both  manometers  were  filled 
with  water  and  both  fittings  were  completed  within  15  minutes  after 
the  root  was  cut.  The  following  records  were  made,  the  figures  show¬ 
ing  —  suction  or  +  pressure  in  mm.  of  Hg.  (Table  2). 


SUCTION  IN  CUT  ENDS  OF  ROOTS  OF  MONTEREY  FINE 


15 


Table  2. 


Date. 

Time. 

Terminal. 

Stump. 

Date. 

Time. 

Terminal. 

Stump. 

1925 

mm. 

1925 

mm. 

July 

17 

3h00m 

p.  m. 

Fittings 

Aug. 

11 

8h  m 

a.  m. 

-  89 

+  o 

made. 

11 

30 

a.  m. 

-  82 

-  0 

3 

15 

p.  m. 

+  5 

+  5 

7 

p.  m. 

-102 

-  0 

4 

p.  m. 

+.  30 

+  8 

Aug. 

12 

7 

30 

a.  m. 

-110 

-  3 

July 

18 

7 

a.  m. 

Air  re- 

+30 

11 

30 

a.  m.1 

-105 

-  0 

leased. 

4 

15 

p.  m. 

-111 

-  0 

11 

30 

a.  m. 

Set  to  0 

+35 

Aug. 

13 

7 

30 

a.  m. 

-100 

-  2 

3 

p.  m. 

-  9 

+30 

11 

30 

a.  m. 

-  93 

-  2 

4 

p.  m. 

-  10 

+25 

7 

p.  m. 

-  86 

-  3 

July 

19 

7 

40 

a.  m. 

-  27 

+24 

Aug. 

14 

5 

45 

a.  m. 

-  80 

-  5 

10 

a.  m. 

-  30 

-  1 

8 

45 

a.  m. 

-  68 

-  4 

5 

p.  m. 

-  41 

-  5 

Aug. 

15 

11 

a.  m. 

-  45 

-  4 

July 

20 

7 

a.  m. 

-  54 

-  8 

Aug. 

16 

7 

30 

a.  m. 

-  43 

-  6 

11 

30 

a.  m. 

-  54 

-  6 

4 

p.  m. 

-  36 

-  5 

3 

30 

p.  m. 

-  60 

-  6 

Aug. 

17 

7 

30 

a.  m. 

-  37 

-  8 

July 

21 

7 

a.  m. 

-  72 

-10 

11 

30 

a.  m. 

-  30 

-  7 

4 

p.  m. 

-  81 

-14 

4 

p.  m. 

-  27 

-  9 

July 

22 

7 

a.  m. 

-  93 

-18 

Aug. 

18 

7 

30 

a.  m. 

-  32 

-  9 

11 

a.  m. 

-  96 

-24 

11 

a.  m. 

-  26 

-  8 

4 

30 

p.  m. 

-  98 

-18 

4 

p.  m. 

-  30 

-  9 

July 

23 

8 

a.  m. 

-108 

-18 

Aug. 

21 

3 

30 

p.  m. 

-  9 

-  9 

11 

45 

a.  m. 

-113 

-20 

Aug. 

22 

8 

a.  m.2 

-  15 

-10 

4 

p.  m. 

-115 

-20 

11 

30 

a.  m.3 

-  8 

July 

24 

7 

30 

a.  m. 

-126 

-24 

5 

p.  m. 

-  4 

4 

p.  m. 

-132 

-24 

Aug. 

23 

8 

a.  m. 

-  8 

8 

p.  m. 

-132 

-24 

11 

a.  m. 

-  13 

July 

25 

7 

30 

a.  m. 

-  69 

-27 

4 

30 

p.  m. 

-  18 

9 

a.  m. 

-  73 

-24 

Aug. 

24 

7 

30 

a.  m. 

-  27 

12 

m. 

-  66 

-24 

11 

a.  m. 

-  24 

3 

p.  m. 

-  66 

-27 

4 

p.  m. 

-  31 

July 

26 

7 

30 

a.  m. 

-  72 

-30 

Aug. 

25 

7 

30 

a.  m. 

-  44 

• 

10 

a.  m. 

-  78 

-28 

11 

30 

a.  m. 

-  39 

3 

p.  m. 

-  83 

-27 

4 

p.  m. 

-  45 

July 

27 

7 

30 

a.  m. 

-  96 

-30 

Aug. 

26 

8 

a.  m. 

-  54 

11 

a.  m. 

-  96 

-29 

11 

30 

a.  m. 

-  54 

2 

30 

p.  m. 

-  98 

-30 

7 

15 

p.  m. 

-  62 

July 

28 

7 

a.  m. 

-110 

-30 

Aug. 

27 

6 

a.  m. 

-  68 

11 

a.  m. 

-108 

-32 

7 

a.  m. 

-  70 

2 

p.  m. 

-107 

-36 

8 

a.  m. 

-  68 

July 

29 

7 

40 

a.  m. 

-108 

-33 

9 

a.  rn. 

-  66 

July 

30 

8 

a.  m. 

-  60 

-28 

10 

a.  m. 

-  65 

4 

p.  m. 

-  57 

-33 

11 

a.  m. 

—  65 

July 

31 

7 

30 

a.  m. 

-  56 

-35 

12 

m. 

-  65 

11 

30 

a.  m. 

-  54 

-33 

2 

p.  m. 

-  68 

Aug. 

2 

3 

45 

p.  m. 

-  54 

-37 

3 

p.  m. 

-  69 

Aug. 

3 

7 

30 

a.  m. 

-  54 

-37 

4 

p.  m. 

-  69 

11 

30 

a.  m. 

-  48 

-36 

5 

p.  m. 

-  72 

3 

40 

p.  m. 

-  50 

-38 

8 

p.  in. 

-  76 

Aug. 

4 

8 

a.  m. 

-  51 

-38 

11 

p.  m. 

-  79 

2 

30 

p.  m. 

-  45 

-39 

Aug. 

28 

3 

a.  m. 

-  80 

Aug. 

5 

9 

a.  m. 

-  51 

-41 

4 

a.  m. 

-  80 

Aug. 

6 

2 

30 

p.  m. 

-  15 

-  0 

6 

a.  m. 

-  80 

Aug. 

7 

9 

a.  m. 

-  39 

+  3 

8 

a.  m. 

-  81 

4 

p.  m. 

-  36 

+  5 

9 

a.  m. 

-  80 

Aug. 

8 

8 

a.  m. 

-  50 

+  2 

10 

a.  m. 

-  79 

4 

p.  m. 

-  54 

+  3 

11 

a.  m. 

-  79 

Aug. 

9 

8 

30 

a.  m. 

-  66 

+  2 

2 

p.  m. 

-  81 

10 

30 

a.  m. 

-  65 

+  1 

4 

p.  m. 

-  81 

7 

p.  m. 

-  72 

+  o 

7 

p.  m. 

-  86 

Aug. 

10 

8 

a.  m. 

-  81 

0 

9 

p.  m. 

-  87 

11 

a.  m. 

-  78 

+  2 

Aug. 

29 

3 

a.  m. 

-  90 

4 

p.  m. 

-  86 

+  1 

4 

a.  m. 

-  90 

1  Soil  about  entire  root  irrigated  for  30  hours.  2  Closed.  3  Air  released;  set  to  0. 


16 


HYDROSTATIC  SYSTEM  OF  TREES 


Table  2 — Continued. 


Date. 

Time. 

Termi¬ 

nal. 

Remarks. 

Date. 

Time. 

Termi¬ 

nal. 

Remarks. 

1925 

1925 

Aug.  29 

6h  m 

a  m. 

-  91 

Oct. 

7 

7h45m 

a.  m. 

-  71 

8 

a.  m. 

-  92 

12 

m. 

-  71 

Aug.  30 

9 

a.  m. 

-  45 

3 

15 

p.  m. 

-  73 

12 

m. 

-  43 

6 

30 

p.  m. 

-  60 

6 

p.  m. 

-  51 

Oct. 

8 

7 

30 

a.  m. 

-  78 

Aug.  31 

9 

a.  m. 

-  62 

4 

p.  m. 

-  84 

4 

p.  m. 

-  65 

Oct. 

9 

7 

30 

a.  m. 

-  90 

Sept.  1 

7 

a.  m. 

-  75 

3 

30 

p.  m. 

-  92 

8 

a.  m. 

-  72 

Oct. 

10 

8 

a.  m. 

-  98 

7 

p.  m. 

-  84 

12 

m. 

-  98 

Sept.  2 

7 

a.  m. 

-  88 

4 

p.  m. 

-101 

11 

a.  m. 

-  82 

Oct. 

11 

8 

a.  m. 

-105 

Sept.  5 

11 

a.  m. 

-  87 

Oct. 

12 

8 

a.  m. 

-115 

6 

30 

p.  m. 

-  97 

4 

p.  m. 

-116 

Sept.  6 

8 

30 

a.  m. 

-  75 

Oct. 

13 

8 

a.  m. 

-134 

6 

p.  m. 

-  50 

2 

p.  m. 

-122 

Sept.  7 

7 

30 

a.  m. 

-  67 

Oct. 

14 

8 

a.  m. 

-126 

11 

15 

a.  m. 

-  58 

Oct. 

16 

9 

a.  m. 

-133 

4 

30 

p.  m. 

-  68 

4 

p.  m. 

-134 

Sept.  8 

7 

30 

a.  m. 

-  80 

Oct. 

17 

9 

a.  m. 

-140 

11 

30 

a.  m. 

-  72 

Oct. 

18 

8 

a.  m. 

-148 

4 

p.  m. 

-  79 

Oct. 

19 

9 

a.  m. 

-156 

Clear. 

Sept.  9 

8 

a.  m. 

-  83 

4 

p.  m. 

-155 

Do. 

11 

30 

a.  m. 

-  69 

Oct. 

20 

7 

30 

a.  m. 

-162 

Do. 

Sept.  10 

7 

30 

a.  m. 

-  57 

2 

p.  in. 

-158 

Do. 

Sept.  13 

8 

a.  m. 

-  27 

Oct. 

21 

8 

a.  m. 

-156 

Do. 

6 

p.  m. 

-  30 

Oct. 

22 

4 

p.  m. 

-159 

Do. 

Sept.  14 

7 

15 

a.  m. 

-  35 

Oct. 

23 

8 

a.  m. 

-  48 

Do. 

11 

30 

a.  m. 

-  17 

11 

a.  m. 

-  44 

Do. 

3 

p.  m.1 

-  23 

Oct. 

24 

7 

a.  m. 

-  66 

Do. 

Sept.  15 

7 

15 

a.  m. 

-  56 

12 

in. 

-  62 

Do. 

3 

30 

p.  m. 

-  56 

7 

p.  m. 

-  72 

Do. 

Sept.  16 

7 

30 

a.  m. 

-  68 

Oct. 

25 

8 

a.  m. 

-  65 

Do. 

Sept.  18 

7 

a.  m. 

-108 

Oct. 

26 

7 

30 

a.  m. 

-  84 

Do. 

Sept.  20 

9 

a.  m. 

-  98 

Oct. 

27 

8 

a.  m. 

-  94 

Overcast. 

Sept.  21 

7 

30 

a.  m. 

-140 

4 

p.  m. 

-  93 

Clear. 

11 

a.  m. 

-138 

Oct. 

28 

7 

30 

a.  m. 

-  99 

Overcast. 

4 

p.  m. 

-139 

4 

p.  m. 

-  98 

Do. 

Sept.  22 

7 

30 

a.  m. 

-  73 

Oct. 

29 

2 

p.  m. 

-102 

Clear. 

11 

30 

a.  m. 

-  62 

Oct. 

30 

7 

30 

a.  m. 

-108 

Overcast. 

5 

30 

p.  m. 

-  72 

Oct. 

31 

8 

a.  m. 

-114 

Do. 

Sept.  23 

8 

a.  m. 

-  81 

Nov. 

1 

10 

30 

a.  m. 

-117 

Do. 

12 

m. 

-  80 

Nov. 

2 

8 

a.  m. 

-125 

Showers. 

4 

p.  m. 

-  84 

Nov. 

3 

9 

a.  in. 

-132 

Clearing. 

Sept.  24 

7 

15 

a.  m. 

-  92 

Nov. 

4 

'  8 

a.  m. 

-124 

Do. 

11 

30 

a.  m. 

-  90 

4 

p.  in. 

-134 

Clear. 

4 

p.  m. 

-  87 

Nov. 

5 

8 

a.  m. 

-144 

Do. 

Sept.  25 

8 

a.  m. 

-  99 

4 

p.  m. 

-140 

5 

p.  m. 

-102 

Nov. 

6 

7 

30 

a.  m. 

-150 

Sept.  26 

7 

15 

a.  m. 

-111 

3 

p.  m. 

-143 

11 

45 

a.  m. 

-118 

Nov. 

7 

8 

a.  m. 

-162 

Clear. 

4 

p.  m. 

-110 

Nov. 

8 

10 

a.  m. 

-149 

Do. 

Sept.  28 

7 

30 

a.  m. 

-  42 

Nov. 

9 

8 

a.  m. 

-137 

Do. 

Sept.  29 

9 

45 

a.  m. 

-  63 

3 

p.  m. 

-151 

Cloudy. 

Sept.  30 

4 

p.  m. 

-  68 

Nov. 

10 

4 

p.  m. 

-146 

Do. 

Oct.  4 

9 

a.  m.2 

-  42 

Nov. 

11 

7 

30 

p.  m. 

-150 

Raining. 

4 

p.  m. 

-  44 

4 

p.  m. 

-139 

Do. 

Oct.  5 

7 

30 

a.  m. 

-  50 

Nov. 

12 

8 

a.  m. 

-114 

Cloudy. 

2 

30 

p.  m. 

-  54 

4 

p.  m. 

-111 

Raining. 

Oct.  6 

7 

30 

a.  m. 

-  61 

Nov. 

13 

7 

30 

a.  m. 

-108 

Clear. 

5 

p.  m. 

-  66 

Nov. 

14 

7 

30 

a.  m. 

-108 

Do. 

1  Air  released;  set  at  —40.  2  Air  released;  set  at  0. 


SUCTION  IN  CUT  ENDS  OF  ROOTS  OF  MONTEREY  PINE. 


17 


Table  2 — Continued. 


Date. 

Time. 

Termi¬ 

nal. 

Remarks. 

Date. 

Time. 

Termi¬ 

nal. 

Remarks. 

1925 

1925 

Nov.  14 

4h  In  p.  m. 

-101 

Clear. 

Nov.  20 

4h30m  p.  m. 

-  99 

Clear. 

Nov.  15 

8  a.  m. 

-  87 

Do. 

Nov.  21 

8  a.  m. 

-111 

Overcast. 

1  30  p.  m. 

-  84 

Do. 

12  rn. 

-  98 

Slightly 

4  p.  m. 

-  86 

Cloudy. 

overcast. 

Nov.  16 

8  a.  m. 

-  86 

Drizzle. 

4  p.  m. 

-100 

Overcast. 

Nov.  17 

7  30  a.  m. 

-  97 

Clear. 

Nov.  22 

8  a.  m. 

-112 

Clear. 

Nov.  18 

7  30  a.  m. 

-101 

Do. 

Nov.  23 

7  30  a.  m. 

-111 

Overcast. 

11  30  a.  m. 

-  94 

Do. 

Nov.  24 

7  30  a.  m. 

-108 

Do. 

2  p.  m. 

-  93 

Do. 

2  p.  m. 

-107 

Clear. 

7  p.  m. 

-  98 

Do. 

Nov.  25 

7  a.  m. 

-115 

Do. 

Nov.  19 

7  30  a.  m. 

-102 

Do. 

2  p.  m. 

-104 

Hazy. 

Nov.  20 

8  a.  m. 

-108 

Do. 

Nov.  26 

12  m. 

-104 

Do. 

11  30  a.  m. 

-  97 

Do. 

Nov.  27 

8  a.  m. 

-120 

Clear. 

2  p.  m. 

-  96 

Do. 

Nov.  28 

8  a.  m. 

-110 

Do. 

Factors  in  Suction  and  Pressure  in  Roots  of  Pinus. 

The  attachment  of  manometers  to  the  distal  ends  of  living  pine 
roots  in  functional  connection  with  trees  would  entail  a  preliminary 
exudation  of  resin  and  the  collapse  of  living  cells  with  an  addition  of 
their  contents  to  the  liquid  bathing  the  surfaces.  Some  elongated 
conduits  in  the  central  part  of  the  stem  might  contain  gases  which 
would  be  displaced  to  some  extent  by  capillary  injection.  Variations 
in  the  volume  and  pressure  of  the  gaseous  contents  of  the  central 
cylinder  of  the  trunk  communicating  with  this  tract  would  give  the 
implied  effects.  It  might  be  expected,  however,  that  the  determining 
feature  would  be  the  pull  from  the  leaves  extending  downward  in  the 
water  column  to  the  liquid  in  the  instrument. 

The  preliminary  action  of  the  smaller  root  (Table  1),  the  woody 
cylinder  of  which  was  only  5  mm.  in  diameter,  showed  no  positive 
pressures,  a  matter  possibly  due  to  size  relations  to  the  instrument  or 
to  defective  fittings.  The  larger  root  exhibited  such  positive  action  in 
the  distal  end  and  on  the  stump  of  the  separated  root.  Exudation 
from  the  separated  root  was  seen  25  days  later.  The  irregularities  of 
the  record  of  the  smaller  root  suggest  defective  fittings,  and  it  was  not 
until  a  fortnight  after  the  beginning  of  the  test  that  reliance  could  be 
placed  on  the  fittings.  After  this  it  may  be  seen  that  on  clear  days 
suction  was  lessened  at  mid-day  in  a  manner  suggestive  of  the  expan¬ 
sion  of  included  gases,  and  that  but  little  variation  was  exhibited  on 
days  which  were  overcast  and  equable.  The  variations,  however, 
were  very  slight,  as  would  be  the  case  with  the  small  amount  of  gas 
which  could  be  included.  The  amount  of  suction  which  reached  a 
maximum  of  —188  mm.  Hg.  =  0.25  atm.,  and  ran  near  this  for  some 
time,  would  be  determined  by  the  tension  in  the  water-column.  The 
greatest  daily  variation  was  only  —8  mm.  Hg.,  and  this  was  late  in 
September  at  a  time  of  greatest  daity  range  of  temperature. 


18 


HYDROSTATIC  SYSTEM  OF  TREES. 


Fig.  6. — Small  tree  of  Monterey  pine  No.  XIII,  which  was  topped  in  April  1925  and  a  manometer 
attached  and  kept  in  adjustment  for  7  months.  Only  a  small  proportion  of  leaves  was 
removed,  and  the  leafy  branches  maintained  a  normal  condition  throughout  the  observations. 


SUCTION  IN  CUT  ENDS  OF  ROOTS  OF  MONTEREY  PINE. 


19 


Following  the  initial  period  in  which  exudation  appeared  and  suc¬ 
tion  was  lessened  in  the  larger  root,  the  daily  increase  in  tension  in  the 
water-column  affected  the  suction,  and  this  continued  for  about  10 
days.  Afterward  the  familiar  cycle  of  change  was  apparent.  This  may 
be  illustrated  by  the  records  of  morning,  noon  and  evening  of  —37, 
—  30  and  —27  on  Aug.  17;  and  of  —80,  —72  and  —79  on  September  8. 
The  greatest  daily  variation  was  equivalent  to  11  mm.  Hg.,  and  the 
maximum  suction  was  — 162  mm.  Hg.  =  0.21  atmospheres  in  November. 
It  was  noted  here  as  in  the  trunk  that,  when  the  instrument  was 
opened  and  reset  to  0,  suction  reached  some  magnitude  at  once,  then 
slowly  increased  to  a  maximum  which  might  not  be  reached  for  many 
days. 

The  tests  of  the  separated  part  of  the  root  were  continued  for  only  36 
days.  Pressures  of  +35  mm.  Hg.  were  exhibited  on  the  first  few  days, 
then  suction  reaching  a  maximum  of  —41  mm.  Hg.  19  days  after  the 
test  was  begun,  to  be  followed  by  positive  pressures  of  +3  mm.  Hg., 
and  low  suction  not  surpassing  10  mm.  Hg.,  which  is  to  be  contrasted 
with  the  action  of  a  separated  root  of  Juglans  discussed  in  a  later 
section  of  this  paper. 

It  was  found  that  an  ample  irrigation  of  the  soil  about  this  root  had 
no  perceptible  effect  on  suction  in  either  portion  of  the  root. 

Variations  in  Suction  at  Top  of  Small  Tree. 

The  removal  of  a  branch  or  the  terminal  of  a  stem  cuts  across  the 
entire  hydrostatic  system  of  the  tree,  various  anatomical  elements 
exposed  being  different  from  those  of  excised  roots.  The  central 
cylinder  containing  gases  is  tapped  more  freely  than  in  an  excised  root. 
This  was  tested  first  in  a  small  tree  about  2  meters  in  height,  which  had 
grown  in  a  shaded  place,  making  thin  annual  layers  of  wood. 

The  above  tree  ( Pinus  radiata,  No.  XIII)  was  topped  at  a  height  of 
110  cm.  from  the  base  and  a  manometer  attached  as  in  figure  6.  This 
instrument  was  replaced  later  by  one  which  made  it  possible  to  release 
air  drawn  from  the  stem.  As  shown  in  figure  6,  six  small  branches 
furnished  a  fairly  adequate  means  of  transpiration.  Records  were 
made  of  suction  in  terms  of  mm.  of  Hg.  (Table  3) . 


20 


HYDROSTATIC  SYSTEM  OF  TREES. 


Table  3. 


Date. 

Time. 

Suction  in 
mm.  Hg. 

Remarks. 

1925 

Apr.  15 

3h15m  a.  m. 

. . 

Attached  within  few  minutes  after  decapitation. 

3  30  p.  m. 

-  16 

3  40  p.  m. 

-  25 

4  10  p.  m. 

-  50 

4  30  p.  m. 

-  66 

Apr.  16 

8  a.  m. 

-172 

10  a.  m. 

-180 

Apr.  17 

8  a.  m. 

-166 

Rubber  tube  was  disconnected  from  stump,  small  sec- 

10  30  a.  m. 

-180 

tion  taken  off,  and  reset  with  Hg.  at  0. 

2  p.  m. 

— 154 

Absorption  pressure  now  fell  and  20  days  later  was  at  0. 

May  14 

8  a.  m. 

-  0 

Instrument  disconnected,  surface  pared,  and  instrument 

2  p.  m. 

-  10 

reset  at  0. 

May  15 

8  a.  m. 

-  4 

May  16 

8  a.  m. 

-  2 

3  a.  m. 

-  2 

Another  section  3  cm.  long  cut  from  end  of  stem,  sur- 

face  being  4  cm.  from  uppermost  pair  of  branches. 

May  17 

8  a.  m. 

-100 

3  30  p.  m. 

-126 

May  18 

8  a.  m. 

-120 

May  19 

2  p.  m. 

-118 

Rain  all  night  and  continuing  day. 

May  20 

8  30  a.  m. 

-120 

3  30  p.  m. 

-120 

May  22 

8  a.  m. 

-104 

May  24 

10  a.  m. 

-  96 

4  p.  m. 

-  60 

May  26 

8  a.  m. 

-  84 

11  30  a.  m. 

-  86 

May  27 

9  a.  m. 

-114 

3  p.  m. 

-116 

May  28 

8  a.  m. 

-126 

11  30  a.  m. 

-120 

May  29 

7  30  a.  m. 

-128 

4  p.  m. 

-128 

Air  bubble  released;  set  to  0. 

May  30 

8  a.  m. 

-  34 

2  p.  m. 

-  50 

May  31 

8  30  a.  m. 

-  82 

Raining. 

11  a.  m. 

-  80 

5  30  p.  m. 

-104 

June  1 

7  a.  m. 

-104 

Raining. 

June  2 

8  a.  m. 

-110 

12  m. 

-106 

Cloudy  followed  by  clearing;  rain  in  night. 

June  3 

7  a.  m. 

-110 

4  p.  m. 

-116 

Clear  and  windy. 

June  4 

8  a.  m. 

-114 

Reset  to  0. 

11  30  a.  m. 

-  14 

June  5 

7  a.  m. 

-  66 

Raining. 

4  p.  m. 

-  84 

June  6 

7  a.  m. 

-110 

Cloudy. 

4  p.  m. 

-120 

Clear. 

June  7 

8  a.  m. 

-140 

Clear. 

June  8 

7  a.  m. 

-136 

Overcast. 

4  p.  m. 

-134 

Clear;  reset. 

June  9 

7  a.  m. 

-  54 

3  p.  m. 

-  90 

Cloudy. 

June  13 

7  a.  m. 

-  90 

Do. 

9  a.  m. 

-  90 

Cloudy;  reset  to  0. 

4  p.  m. 

-  20 

June  14 

8  a.  m. 

-  44 

Cloudy. 

9  a.  m. 

-  36 

June  15 

8  3i.  m. 

-  46 

2  p.  m. 

-  50 

Clear. 

SUCTION  IN  CUT  ENDS  OF  ROOTS  OF  MONTEREY  PINE 


21 


Table  3 — Continued. 


Date. 

Time. 

Suction  in 
mm.  Hg. 

Remarks. 

1925 

June 

16 

8h  m 

a.  m. 

-  66 

Cloudy. 

4 

p.  m. 

-  60 

Do. 

June 

17 

9 

a.  m. 

-  80 

Do. 

12 

m. 

-  80 

Do. 

4 

p.  m. 

-  84 

Do. 

June 

18 

3 

p.  m. 

-110 

Cloudy. 

June 

19 

7 

a.  m. 

-118 

Clear. 

11  30 

a.  m. 

-  76 

Clouding. 

2  30 

p.  m. 

-  90 

Clearing. 

June  20 

8 

a.  m. 

-106 

Fog. 

12 

m. 

-110 

Do. 

4 

p.  m. 

-114 

Do. 

June  21 

8 

a.  m. 

-  84 

Fog;  reset  to  0. 

12 

m. 

-  10 

Fog. 

June  22 

7 

a.  m. 

-  44 

Clearing. 

10 

a.  m. 

-  40 

4 

p.  m. 

-  54 

Clear. 

June  23 

8 

a.  m. 

-  60 

Do. 

10  30 

a.  m. 

-  76 

Do. 

June  24 

7 

a.  m. 

-100 

Do. 

11 

a.  m. 

-106 

2 

p.  m. 

-  90 

Clear. 

June  25 

7 

a.  m. 

-  88 

Do. 

12 

m. 

-110 

Do. 

4 

p.  m. 

-100 

Do. 

June  26 

7 

a.  m. 

-132 

4  30 

p.  m. 

-  96 

June  27 

8 

a.  m. 

-  96 

Cloudy. 

3 

p.  m. 

-100 

Do. 

June  28 

8 

a.  m. 

-100 

4 

p.  m. 

-100 

Cool. 

June  29 

9 

a.  m. 

-104 

Do. 

4 

p.  m. 

-106 

Do. 

June  30 

7 

a.  m. 

-104 

Air  released ;  set  to  0. 

June  30 

2 

p.  m. 

-  3 

Clear. 

July 

1 

7 

a.  m. 

-  6 

Do. 

8 

p.  m. 

-  6 

Fog. 

July 

2 

7 

a.  m. 

-  24 

Do. 

7 

p.  m. 

-  26 

Do. 

July 

3 

7 

a.  m. 

-  28 

Reset  to  0. 

2  30 

p.  m. 

-  0 

5 

p.  m. 

-  0 

Fog. 

July 

4 

9 

a.  m. 

-  9 

Do. 

11 

a.  m. 

-  0 

Sunny. 

3  30 

p.  m. 

-  12 

Sunny. 

July 

5 

8  30 

a.  m. 

-  18 

Overcast. 

10  30 

a.  m. 

-  8 

Clear. 

4  30 

p.  m. 

-  21 

Do. 

July 

6 

7 

a.  m. 

-  20 

Do. 

11 

a.  m. 

-  10 

Do. 

6  30 

p.  m. 

-  10 

Do. 

July 

7 

7 

a.  m. 

-  18 

Overcast. 

9 

a.  m. 

-  18 

Do. 

2 

p.  m. 

-  10 

Sunny. 

4 

p.  m. 

-  15 

Do. 

July 

8 

7  30 

a.  m. 

-  15 

Air  released;  reset  to  0. 

2 

p.  m. 

-  2 

4 

p.  m. 

-  4 

July 

9 

7  30 

a.  m. 

-  6 

Fog  and  drizzle. 

10  30 

a.  m. 

-  6 

Do. 

4 

p.  m. 

-  4 

Overcast. 

July 

11 

7  30 

a.  m. 

-  6 

Clear. 

11 

a.  m. 

-  3 

Do. 

22 


HYDROSTATIC  SYSTEM  OF  TREES 


Table  3 — Continued. 


Date. 

Time. 

Suction  in 
mm.  Hg. 

Remarks. 

1925 

July  11 

2h30m 

p.  m. 

-  3 

Clear. 

4  30 

p.  m. 

-  8 

Do. 

July  12 

8 

a.  m. 

-  7 

Do. 

10  30 

a.  m. 

-  3 

Do. 

July  13 

7  30 

a.  m. 

-  10 

Do. 

9  30 

a.  m. 

-  7 

Do. 

12 

m. 

-  6 

Do. 

3  30 

p.  m. 

-  10 

Do. 

July  14 

7  30 

a.  m. 

-  11 

Do. 

11  15 

a.  m. 

-  10 

Clouds  and  sunshine. 

2  15 

p.  m. 

-  12 

Do. 

July  15 

7  30 

a.  m. 

-  14 

Foggy. 

9  30 

a.  m. 

-  12 

Clear. 

July  16 

1  30 

7 

p.  m. 

a.  m. 

-  14 

-  14 

Clear. 

11 

a.  m. 

-  10 

Do. 

3  30 

p.  m. 

-  14 

Do. 

July  17 

7 

a.  m. 

-  14 

Do. 

3  15 

p.  m. 

-  15 

Do. 

July  18 

7 

a.  m. 

-  18 

Clouds. 

11  30 

a.  m. 

-  18 

Do. 

4 

p.  m. 

-  18 

Do. 

July  19 

7  40 

a.  m. 

-  20 

Do. 

10 

a.  m. 

-  23 

Do. 

5 

p.  m. 

-  20 

Cloudy. 

July  20 

7 

a.  m. 

-  20 

Cloudy;  taken  down,  a  few  mm.  sliced  from  end  and 

11  30 

a.  m. 

-  2 

reset  at  0. 

Clouds. 

3  30 

p.  m. 

-  5 

Clear. 

July  21 

7 

a.  m. 

-  14 

Overcast. 

11 

a.  m. 

-  14 

Do. 

4 

p.  m. 

-  15 

Clouds. 

July  22 

7 

a.  m. 

-  21 

Drizzling. 

11 

a.  m. 

-  24 

Do. 

4  30 

p.  m. 

-  23 

Overcast. 

July  23 

8 

a.  m. 

-  27 

Warmer. 

11  45 

a.  m. 

-  27 

Clear. 

4 

p.  m. 

-  30 

Do. 

July  24 

7  30 

a.  m. 

-  36 

Cloudy. 

4 

p.  m. 

-  38 

Clouds  and  sunshine. 

8 

p.  m. 

-  38 

Do. 

July  25 

7  30 

a.  m. 

-  44 

Overcast. 

9 

a.  m. 

-  43 

Clear. 

12 

m. 

-  42 

Do. 

3 

p.  m. 

-  43 

Clouds. 

July  26 

7  30 

a.  m. 

-  51 

Fog. 

10 

a.  m. 

-  50 

Overcast. 

3 

p.  m. 

-  51 

Do. 

July  27 

7  30 

a.  m. 

-  56 

Do. 

11  30 

a.  m. 

-  56 

Do. 

3  30 

p.  m. 

-  57 

Do. 

July  28 

7 

a.  m. 

-  60 

Do. 

11 

a.  m. 

-  62 

Do. 

2 

p.  m. 

-  62 

Sunny. 

July  29 

7  40 

a.  m. 

-  68 

Overcast. 

July  30 

8 

a.  m. 

-  72 

Dripping  fog. 

4 

p.  m. 

-  79 

Overcast. 

July  31 

7  30 

a.  m. 

-  78 

Do. 

July  31 

11  30 

a.  m. 

-  78 

Clearing. 

Aug.  2 

3  45 

p.  m. 

-  92 

Clear. 

Aug.  3 

7  30 

a.  m. 

-  97 

Overcast. 

11  30 

a.  m. 

-  98 

Clear. 

3  40 

a.  m. 

-  98 

Do. 

SUCTION  IN  CUT  ENDS  OF  ROOTS  OF  MONTEREY  PINE 


23 


Table  3 — Continued. 


Date. 

Time. 

Suction  in 
mm.  Hg. 

Remarks. 

1925 

Aug.  4 

8h  m  a.  m. 

-104 

Overcast. 

2  30  p.  m. 

-104 

Sunny. 

Aug.  5 

9  a.  m. 

-110 

Fog. 

Aug.  6 

2  30  p.  m. 

-117 

Sunshine. 

Aug.  7 

9  a.  m. 

-125 

Fog. 

4  p.  m. 

-138 

Sunny. 

Aug.  8 

8  a.  m. 

-132 

Foggy. 

4  p.  m. 

-134 

Aug.  9 

8  30  a.  m. 

-138 

Overcast. 

7  p.  m. 

-144 

Do. 

Aug.  10 

8  a.  m. 

-146 

.  Do. 

11  a.  m. 

-146 

Clear. 

4  p.  m. 

-149 

Do. 

Aug.  11 

8  a.  m. 

-153 

Do. 

11  30  a.  m. 

-145 

Do. 

7  p.  m. 

-160 

Do. 

Aug.  12 

7  30  a.  m. 

-162 

Do. 

11  30  a.  m. 

-164 

Do. 

4  15  p.  m. 

-165 

Do. 

Aug.  13 

7  30  a.  m. 

-170 

Overcast. 

11  30  a.  m. 

-170 

7  p.  m. 

-174 

Clear  in  afternoon. 

Aug.  14 

5  45  a.  m. 

-178 

Overcast. 

8  45  a.  m. 

-176 

Clearing. 

Aug.  15 

11  a.  m. 

-186 

Overcast. 

Aug.  16 

7  30  a.  m. 

-190 

Do. 

4  p.  m. 

-192 

Do. 

Aug.  17 

7  30  a.  m. 

-198 

Do. 

11  30  a.  m. 

-189 

Clear  at  9h30Da  a.  m. 

4  p.  m. 

-204 

Aug.  18 

7  30  a.  m. 

-204 

11  a.  m. 

-204 

4  p.  m. 

-206 

Aug.  19 

7  a.  m. 

-210 

Clear. 

4  15  p.  m. 

-210 

Aug.  20 

7  30  a.  m. 

-213 

U  tube  replaced  by  vertical  column  and  reset  at  0. 

Aug.  21 

3  30  p.  m. 

-  16 

Aug.  22 

8  a.  m. 

-  20 

Clear. 

11  30  a.  m. 

-  20 

Do. 

5  p.  m. 

-  23 

Do. 

Aug.  23 

8  a.  m. 

-  27 

Misting. 

11  a.  m. 

-  32 

Clearing. 

4  30  p.  m. 

-  30 

Sunny. 

Aug.  24 

7  30  a.  m. 

-  35 

Do. 

11  30  a.  m. 

-  33 

Do. 

4  p.  m. 

-  37 

Do. 

Aug.  25 

7  30  a.  m. 

-  60 

Clear. 

11  30  a.  m. 

-  42 

Do. 

4  p.  m. 

-  47 

Do. 

Aug.  26 

8  a.  m. 

-  50 

Overcast. 

11  30  a.  m. 

-  57 

Beginning  to  clear. 

7  15  p.  m. 

-  50 

Overcast. 

Aug.  27 

6  a.  m. 

-  53 

7  a.  m. 

-  55 

8  a.  m. 

-  54 

9  a.  m. 

-  54 

10  a.  m. 

-  55 

11  a.  m. 

-  55 

12  m. 

-  55 

2  p.  m. 

-  56 

3  p.  m. 

-  55 

4  p.  m. 

-  56 

5  p.  m. 

-  58 

24 


Date. 

1925 
Aug.  27 

Aug.  28 


Aug.  29 

Aug.  30 
Aug.  30 

Aug.  31 

Sept.  1 

Sept.  2 
Sept.  5 
Sept.  6 
Sept.  7 

Sept.  8 

Sept.  9 

Sept.  10 
Sept.  13 

Sept.  14 

Sept.  15 

Sept.  16 
Sept.  18 
Sept.  20 
Sept.  21 

Sept.  22 

Sept.  23 

Sept.  24 

Sept.  25 


HYDROSTATIC  SYSTEM  OF  TREES. 


Table  3 — Continued. 


Time. 

Suction  in 
mm.  Hg. 

Remarks. 

8h  m 

p.  m. 

-  60 

11 

p.  m. 

-  58 

3 

a.  m. 

-  58 

4 

a.  m. 

-  60 

6 

a.  m. 

-  60 

8 

a.  m. 

-  60 

9 

a.  m. 

-  61 

10 

a.  m. 

-  62 

11 

a.  m. 

-  62 

2 

p.  m. 

-  63 

4 

p.  m. 

-  63 

7 

p.  m. 

-  65 

9 

p.  m. 

-  66 

3 

a.  m. 

-  70 

4 

a.  m. 

-  74 

6 

a.  m. 

-  66 

8 

a.  m. 

-  68 

9 

a.  m. 

-  75 

Fog. 

12 

m. 

-  70 

Sunny. 

6 

p.  m. 

-  78 

Do. 

9 

a.  m. 

-  80 

Do. 

4 

p.  rn. 

-  82 

Do. 

7 

a.  m. 

-  86 

Clouds. 

12 

m. 

-  88 

Sunny. 

7 

p.  m. 

-  94 

Clear. 

7 

a.  m. 

-  92 

Clearing. 

11 

a.  m. 

-  93 

Clear. 

11 

a.  m. 

-112 

6  30 

p.  in. 

-117 

Clear. 

8  30 

a.  m. 

-120 

Clearing  after  shower. 

6 

p.  m. 

-124 

Clouds. 

7  30 

a.  m. 

-126 

Clearing  after  shower. 

11  15 

a.  m. 

-128 

Clear. 

4  30 

p.  m. 

-128 

Do. 

7  30 

a.  m. 

-132 

Do. 

11  30 

a.  m. 

-131 

Do. 

4 

p.  m. 

-135 

Do. 

8 

a.  m. 

-137 

Cloudy. 

11  30 

a.  m. 

-136 

Clear. 

7  30 

a.  m. 

-142 

Cloudy. 

8 

a.  m. 

-151 

Clearing. 

6 

p.  m. 

-156 

Clear. 

7  15 

a.  m. 

-156 

Do. 

11  30 

a.  m. 

-154 

Do. 

4 

p.  m. 

-155 

Do. 

7  15 

a.  m. 

-158 

Do. 

3  30 

p.  m. 

-157 

Do. 

7  30 

a.  m. 

-162 

Some  clouds. 

7 

a.  m. 

-171 

Clouds;  rain  on  17th. 

9 

a.  m. 

-173 

Clear. 

7  30 

a.  m. 

-177 

Do. 

11  30 

a.  m. 

-175 

Do. 

4 

p.  m. 

-176 

Do. 

7  30 

a.  m. 

-194 

Do. 

11  30 

a.  m. 

-178 

Do. 

5  30 

p.  m. 

-180 

Cloudy. 

8 

a.  m. 

-182 

Do. 

12 

in. 

-183 

Do. 

4 

p.  m. 

-181 

Do. 

7  15 

a.  m. 

-185 

Overcast. 

11  30 

a.  m. 

-184 

Clearing. 

4 

p.  m. 

-183 

Clouds. 

8 

a.  m. 

-186 

Clear. 

5 

p.  m. 

-186 

Do. 

SUCTION  IN  CUT  ENDS  OF  ROOTS  OF  MONTEREY  PINE. 


25 


Table  3 — Continued. 


Date. 

Time. 

Suction  in 
mm.  Hg. 

Remarks. 

1925 

Sept.  26 

7h15m  a.  m. 

-187 

Clear. 

11  45  a.  m. 

-186 

Do. 

Sept.  28 

7  30  a.  m. 

-192 

Some  clouds. 

Sept.  29 

9  45  a.  m. 

-193 

Clear. 

Sept.  20 

4  p.  m. 

-191 

Do. 

Oct.  4 

9  a.  m. 

-193 

Do. 

4  p.  m. 

-194 

Do. 

Oct.  5 

7  30  a.  m. 

-197 

Do. 

2  30  p.  m. 

-194 

Clouds. 

Oct.  6 

7  30  a.  m. 

-198 

Clear. 

5  p.  m. 

-179 

Do. 

Oct.  7 

7  45  a.  m. 

-187 

Clear. 

12  m. 

-179 

Do. 

3  15  p.  m. 

-182 

Do. 

6  30  p.  m. 

-185 

Do. 

Oct.  8 

7  30  a.  m. 

-189 

Do. 

4  p.  m. 

-183 

Do. 

Oct.  9 

7  30  a.  m. 

-187 

Cloudy. 

3  30  p.  m. 

-185 

Do. 

Oct.  10 

8  a.  m. 

-187 

Do. 

12  m. 

-184 

Overcast. 

4  p.  m. 

-184 

Do. 

Oct.  11 

8  15  a.  m. 

-185 

Cloudy  for  2  days. 

Oct.  12 

8  a.  m. 

-188 

Cloudy;  rainy  since  noon  of  11th. 

4  p.  m. 

-184 

Cloudy  and  sun. 

Oct.  13 

8  a.  m. 

-188 

Clear  and  cold. 

2  p.  m. 

-184 

Do. 

Oct.  14 

8  a.  m. 

-188 

Do. 

Oct.  16 

9  a.  m. 

-188 

Cloudy. 

4  p.  m. 

-185 

Do. 

Oct.  17 

8  a.  m. 

-188 

Cloudy;  since  15th. 

Oct.  18 

8  a.  m. 

-190 

Clear. 

Oct.  19 

8  a.  m. 

-188 

Do. 

4  p.  m. 

-182 

Do. 

Oct.  20 

7  30  a.  m. 

-187 

2  p.  m. 

-183 

Clear. 

Oct.  21 

8  a.  m. 

-185 

Do. 

Oct.  22 

4  p.  m. 

-186 

Do. 

Oct.  23 

7  a.  m. 

-188 

Do. 

11  a.  m. 

-186 

Do. 

Oct.  24 

7  p.  m. 

-190 

Clear. 

12  m. 

-187 

Do. 

7  p.  m. 

-186 

Do. 

Oct.  25 

8  a.  m. 

-187 

Do. 

Oct.  26 

7  30  a.  m. 

-187 

Overcast. 

Oct.  27 

8  a.  m. 

-190 

Do. 

4  p.  m. 

-189 

Clear. 

Oct.  28 

7  30  a.  m. 

-192 

Overcast. 

4  p.  m. 

-190 

Do. 

Oct.  29 

2  p.  m. 

-189 

Clear. 

Oct.  30 

7  30  a.  m. 

-192 

Overcast. 

Oct.  31 

8  a.  m. 

-191 

Do. 

Nov.  1 

10  30  a.  m. 

-191 

Do. 

Nov.  2 

8  a.  m. 

-194 

Showers. 

Nov.  3 

9  a.  m. 

-196 

Clear. 

Nov.  4 

8  a.  m. 

-196 

Do. 

4  p.  m. 

-194 

Do. 

Nov.  5 

8  a.  m. 

-197 

Do. 

4  p.  m. 

-194 

Do. 

Nov.  6 

8  a.  m. 

-198 

Do. 

3  p.  m. 

-195 

Do. 

Nov.  7 

8  a.  m. 

-198 

Do. 

26 


HYDROSTATIC  SYSTEM  OF  TREES. 


Table  3 — Continued. 


Date. 

Time. 

Suction  in 
mm.  Hg. 

Remarks. 

1925 

Nov.  8 

10h  m  a.  m. 

-194 

Clear. 

Nov.  9 

8  a.  m. 

-197 

Cloudy. 

Nov.  10 

4  p.  m. 

-143 

Do. 

Nov.  11 

7  30  a.  m. 

-194 

Raining. 

4  p.  m. 

-193 

Do. 

Nov.  12 

8  a.  m. 

-195 

Cloudy. 

Nov.  12 

4  p.  m. 

-193 

Raining. 

Nov.  13 

7  30  a.  m. 

-197 

Clear. 

Nov.  14 

7  30  a.  m. 

-197 

Do. 

4  p.  m. 

-193 

Do. 

Nov.  15 

8  a.  m. 

-195 

Do. 

1  30  p.  m. 

-190 

Do. 

6  p.  m. 

-192 

Cloudy. 

Nov.  16 

8  a.  m. 

-191 

Drizzle. 

Nov.  17 

7  30  a.  m. 

-195 

Clear. 

Nov.  18 

7  30  a.  m. 

-195 

Do. 

11  30  a.  m. 

-188 

Do. 

2  p.  m. 

-189 

Do. 

7  p.  m. 

-190 

Do. 

Nov.  19 

7  30  a.  m. 

-192 

Do. 

Nov.  20 

8  a.  m. 

-192 

Do. 

11  30  a.  m. 

-182 

Do. 

2  p.  m. 

-183 

Do. 

4  30  p.  m. 

-193 

Do. 

Nov.  21 

8  a.  m. 

-191 

Overcast. 

12  m. 

-185 

Slightly  overcast. 

4  p.  m. 

-185 

Overcast. 

Nov.  22 

8  a.  m. 

-191 

Clear. 

Nov.  23 

7  30  a.  m. 

-187 

Overcast. 

Nov.  24 

7  30  a.  m. 

-188 

Do. 

2  p.  m. 

-185 

Clear. 

Nov.  25 

7  a.  m. 

-192 

Do. 

2  p.  m. 

-187 

Hazy. 

Nov.  26 

12  m. 

-186 

Do. 

Nov.  27 

8  a.  m. 

-190 

Clear. 

Nov.  28 

8  a.  m. 

-188 

Do. 

In  the  earlier  part  of  the  test  the  irregularities  and  wide  range  of 
suction  may  be  attributed  in  part  to  faulty  fittings.  It  is  apparent, 
however,  that  the  greatest  suction  might  come  at  mid-day  as  deter¬ 
mined  by  the  tension  on  the  water  column.  Much  air  was  drawn  from 
the  stem  at  times.  The  low  record  during  the  first  20  days  of  July 
may  be  taken  as  being  due  to  defective  connections.  When  this  fault 
was  repaired  an  irregular  increase  of  suction  followed,  which  continued 
for  20  days,  reaching  a  seasonal  maximum  of  213  mm.  Hg.  =0.28  atm. 

The  capacity  of  the  instrument  having  been  reached  a  replacement 
was  made  and  suction  climbed  to  a  maximum  of  —198  mm.  Hg.  in 
56  days.  It  remained  near  this  point  to  the  close  of  the  observations. 
The  amount  of  suction  must  be  attributed  to  the  tension  in  the  water 
column  and  its  daily  variations  to  the  changes  in  pressure  of  the 
enclosed  gases  under  the  influence  of  temperature.  This  variation 
was  especially  notable  in  all  tests  on  November  20,  when  the  records 
in  this  tree  were  —192,  182  and  193,  morning,  noon  and  evening.  A 
record  of  198,  189  and  204  represents  the  maximum  daily  range  of 
variation. 


SUCTION  AND  PRESSURE  IN  TRUNKS  OF  PINE. 


27 


SUCTION  AND  PRESSURE  IN  OUTER  LAYERS  OF  TRUNKS 

OF  LARGE  PINE  TREES. 


This  tree  ( Pinus  radiata,  No.  28,  Dendrographic  series)  has  been 
under  dendrographic  measurement  since  1924  (fig.  7).  The  trunk  had 


Fig.  7. — Monterey  pine  (No.  28  of  Dendrographic  series)  with  manometer  attached  to  radial  bore 
which  tapped  some  older  wood.  Observations  begun  April  1925  and  continued  for  7  months. 
Suction  as  great  as  0.5  atm.  was  registered. 


28 


HYDROSTATIC  SYSTEM  OF  TREES. 


a  diameter  of  about  80  cm.  and  was  approaching  maturity.  The 
layers  of  wood  formed  annually  were  not  more  than  1  to  2  mm.  in 
thickness.  No  test  could  be  made  as  to  the  hollow  cylindrical  column 
of  ascending  sap,  but  it  may  be  safely  assumed  that  a  tangential  bore 
driven  to  a  depth  of  8  cm.  at  a  distance  of  80  cm.  from  the  base,  con- 


Fig.  8. — Threaded  tubes  used  in  bores  for  extraction  of  sap  and  for 
attachment  of  manometers.  A,  small  tube  for  extracting  sap 
from  separate  layers  of  wood  of  pine  trees.  D,  larger  tube  with 
set  nut  collar  for  general  extraction.  B,  section  of  brass  tube 
with  threaded  end  for  general  use  in  attachment  of  man¬ 
ometers  to  bores.  C,  tube  with  tapering  threaded  end  for 
secure  fixation  in  bores  with  square  section  to  facilitate  fixation 
by  screwing  firmly  into  bore. 


nected  not  only  the  sap-carrying  layer  (fig.  1  B)  but  also  the  inner 
cylinder  filled  with  air  (fig.  1  D).  The  first  manometer  was  of  the 
type  with  closed  end  so  that  absorption  pressure  would  be  denoted  by  a 
shortened  air-column,  and  suction  by  a  lengthened  one.  Later,  an 
open-arm  manometer,  then  a  single  upright  tube  stepped  in  a  dish  of 
mercury,  were  used  as  noted.  Readings  were  as  shown  in  Table  4. 


SUCTION  IN  TRUNKS  OF  MONTEREY  PINE. 


29 


Table  4. 


Date. 

Time. 

Length  of 
air-column 
in  closed 
end  of 
manometer 
in  mm.  Hg. 

Remarks. 

1925 

Apr.  15 

8h05m  a.  m. 

80 

In  attachment  of  instrument  a  few  minutes  elapsed  after 

8  08  a.  m. 

83 

water  is  poured  into  borehole  before  column  could  be 

8  10  a.  m. 

84 

measured.  This  error,  however,  could  not  amount 

8  15  a.  m. 

85 

to  more  than  1  to  2  mm.  Hg. 

8  25  a.  m. 

85 

8  30  a.  m. 

85 

8  45  a.  m. 

87 

9  a.  m. 

88 

9  30  a.  m. 

88 

12  m. 

87 

2  30  p.  m. 

68 

Apr.  15 

4  30  p.  m. 

52 

Apr.  16 

8  a.  m. 

26 

=3.2  atm.  exudation  pressure. 

10  a.  m. 

26 

Apr.  17 

8  a.  m. 

26 

Refitted  and  cleaned  out;  not  much  resin;  air-column 

77  mm. 

10  30  a.  m. 

68 

Tube  as  in  fig.  8  D  screwed  into  bore. 

2  p.  m. 

67 

3  p.  m. 

67 

Apr.  18 

3  p.  m. 

100 

Suction. 

Apr.  19 

9  a.  m. 

Apr.  20 

9  a.  m. 

100 

Apr.  21 

9  a.  m. 

51 

Apr.  22 

9  a.  m. 

50 

No  significant  variation  in  20  days  following. 

July  4 

4  p.  m. 

150 

Much  air  in  column,  but  liquid  in  cavity;  new  man- 

ometer  with  open  arm  fitted  after  replacing  watery 

contents  of  bore  which  contained  dense  clumps  of 

resinous  material. 

Suction 

or 

pressure 

mm.  Hg. 

July  4 

4  15  p.  m. 

-  8 

Sunny. 

July  5 

8  30  a.  m. 

-  38 

Overcast;  air  released;  set  to  0. 

10  30  a.  m. 

+  5 

Clear. 

4  30  p.  m. 

-  6 

Do. 

July  6 

7  a.  m. 

-  30 

11  a.  m. 

-  27 

Clear. 

7  30  p.  m. 

-  39 

Do. 

July  7 

7  a.  m. 

-  62 

Overcast. 

9  *  a.  m. 

-  63 

Do. 

2  p.  m. 

-  62 

Sunny;  air  released;  set  at  0. 

4  p.  m. 

-  3 

Sunny. 

July  8 

7  30  a.  m. 

-  6 

Overcast. 

9  30  a.  m. 

-  3 

Clearing;  air  released,  and  reset  to  0. 

2  p.  m. 

-  5 

4  p.  m. 

-  6 

Overcast. 

July  9 

7  30  a.  m. 

-  3 

Fog  and  drizzle. 

10  30  a.  m. 

-  3 

Do. 

4  p.  m. 

-  3 

Overcast. 

July  11 

7  30  a.  m. 

-  8 

Air  released  and  set  to  0. 

11  a.  m. 

-  0 

Clear. 

2  30  p.  m. 

-  7 

Do.  - 

4  30  p.  m. 

-  12 

Do. 

July  12 

8  a.  m. 

-  33 

Do. 

10  30  a.  m. 

-  32 

Do. 

30 


HYDROSTATIC  SYSTEM  OF  TREES 


Table  4 — Continued. 


Date. 

Time. 

Suction 

or 

pressure 

in 

mm.  Hg. 

Remarks. 

1925 

July 

13 

7h30m 

a.  m. 

-  70 

Clear. 

9 

30 

a.  m. 

-  72 

Do. 

12 

m. 

-  74 

Do. 

3 

30 

p.  m. 

-  78 

Do. 

July 

14 

7 

30 

a.  m. 

-103 

Do. 

11 

15 

a.  m. 

-108 

Alternating  cloud  and  sunshine. 

2 

15 

p.  m. 

-110 

Do. 

July 

15 

7 

30 

a.  m. 

-138 

Foggy. 

9 

30 

a.  m. 

-138 

Clear. 

• 

1 

30 

p.  m. 

-139 

Do. 

July 

16 

7 

a.  m. 

-116 

Do. 

11 

a.  m. 

-115 

Do. 

3 

30 

p.  m. 

-  79 

Do. 

July 

17 

7 

a.  m. 

-105 

Do. 

3 

15 

p.  rn. 

-  75 

Do. 

July 

18 

7 

a.  m. 

-  66 

Clouds. 

11 

30 

a.  m. 

-  63 

Do. 

4 

p.  m. 

-  55 

Do. 

July 

19 

7 

04 

a.  m. 

-  35 

Clouds;  air  out;  reset  to  0. 

10 

a.  m. 

-  5 

5 

p.  m. 

-  18 

Cloudy. 

July 

20 

7 

a.  m. 

-  38 

Do. 

11 

30 

a.  m. 

-  42 

Do. 

3 

30 

a.  m. 

-  45 

Clear. 

July 

21 

7 

a.  m. 

-  60 

Overcast. 

11 

a.  m. 

-  74 

Do. 

4 

p.  m. 

-  84 

Clouds  and  sun. 

July 

22 

7 

a.  m. 

-103 

Drizzling. 

11 

a.  m. 

-107 

Do. 

4 

30 

p.  m. 

-110 

Overcast. 

July 

23 

8 

a.  m. 

-127 

Do. 

11 

45 

a.  m. 

-132 

Clear. 

4 

p.  m. 

-138 

Do. 

July 

24 

7 

30 

a.  m. 

-160 

Cloudy. 

4 

p.  m. 

-172 

Clouds  and  sunshine. 

8 

p.  m. 

-174 

Limit  of  U  tube. 

July 

25 

7 

30 

a.  m. 

-182 

Overcast. 

9 

a.  m. 

-180 

Clear. 

12 

m. 

-184 

Do. 

3 

p.  m. 

-184 

Clouds. 

July 

26 

7 

30 

a.  m. 

-186 

U  tube  replaced  by  vertical  column.  Reset  at  —160. 

10 

a.  m. 

-148 

Overcast. 

3 

p.  m. 

-145 

Do. 

July 

27 

7 

30 

a.  m. 

-158 

Do. 

11 

30 

a.  m. 

-155 

Do. 

2 

30 

p.  m. 

-160 

Do. 

July 

28 

7 

a.  m. 

-174 

Do. 

11 

a.  m. 

-174 

Do. 

2 

p.  m. 

-175 

Sunny. 

July 

29 

7 

45 

a.  m. 

-195 

Overcast. 

July 

30 

8 

a.  m. 

-215 

Dripping  fog. 

4 

p.  m. 

-212 

Overcast. 

July 

31 

7 

30 

a.  m. 

-235 

Do. 

11 

30 

a.  m. 

-232 

Clearing. 

Aug. 

2 

4 

p.  m. 

. .  ,  ,  . 

Connections  faulty  and  were  not  restored  until  5  days 

later,  when  -stopcocks  were  left  open  and  amount  of 

water  absorbed  was  measured. 

Aug. 

6 

4 

p.  m. 

......... 

Set  at  0. 

Aug. 

7 

4 

p.  m. 

2.5  ml.  water  absorbed. 

Aug. 

8 

4 

p.  m. 

1.2  ml.  water  absorbed. 

SUCTION  IN  TRUNKS  OF  MONTEREY  PINE 


31 


Table  4 — Continued. 


Date. 

Time. 

Suction 

or 

pressure 

in 

mm.  Hg. 

Remarks. 

1925 

Aug.  9 

7h  m  p.  m. 

1.5  ml.  water  absorbed. 

Aug.  10 

4  p.  m. 

•  •••••••a 

1.2  ml.  water  absorbed. 

6.4  ml.  -water  absorbed  in  96  hours.  Stopcocks  closed  to 

measure  suction. 

Aug.  11 

8  a.  m. 

-  54 

11  30  a.  m. 

-  58 

Clear. 

7  p.  m. 

-  75 

Do. 

Aug.  12 

7  30  a.  m. 

-  95 

Clear. 

11  30  a.  in. 

-100 

Do. 

4  15  p.  m. 

-112 

Do. 

Aug.  13 

7  30  a.  m. 

-138 

Overcast. 

11  30  a.  m. 

-145 

Do. 

7  p.  m. 

-160 

Sun  in  afternoon. 

Aug.  14 

5  45  a.  m. 

-177 

Overcast. 

8  45  a.  m. 

-177 

Clearing. 

Aug.  15 

11  a.  m. 

-210 

Overcast. 

Aug.  16 

7  30  a.  m. 

-232 

Do. 

4  p.  m. 

-245 

Do. 

Aug.  17 

7  30  a.  m. 

-256 

Do. 

11  30  a.  m. 

-256 

Clear  at  9h30m. 

4  p.  m. 

-293 

Clear. 

Aug.  18 

7  30  a.  m. 

-280 

Do. 

11  a.  m. 

-275 

Do. 

4  p.  m. 

-280 

Do. 

Aug.  19 

7  a.  m. 

-295 

Do. 

11  45  a.  m. 

-262 

Do. 

4  15  p.  m. 

-292 

Do. 

Aug.  20 

7  30  a.  m. 

-  50 

Fittings  defective. 

Aug.  22 

8  a.  m. 

-  0 

Reset  at  —50. 

Aug.  23 

8  a.  m. 

-  65 

Misting. 

11  15  a.  m. 

-  63 

Clearing. 

4  30  p.  m. 

-  70 

Clear. 

Aug.  24 

7  30  a.  m. 

-  66 

Do. 

11  30  a.  m. 

-  63 

4  p.  m. 

-  72 

Do. 

Aug.  25 

7  30  a.  m. 

-  75 

Do. 

11  30  a.  m. 

-  73 

Do. 

4  p.  m. 

-  78 

Do. 

Aug.  26 

8  a.  m. 

-  92 

Overcast. 

11  30  a.  m. 

-  92 

Beginning  to  clear. 

7  15  p.  m. 

-  95 

Overcast. 

Aug.  27 

6  a.  m. 

-  99 

7  a.  m. 

-  97 

8  a.  m. 

-  90 

9  a.  m. 

-  92 

10  a.  m. 

-  91 

12  m. 

-  92 

2  p.  m. 

-  93 

3  p.  m. 

-  93 

4  p.  m. 

-  96 

5  p.  m. 

-  97 

8  p.  m. 

-  97 

11  p.  m. 

-102 

* 

Aug.  28 

3  a.  m. 

-103 

4  a.  m. 

-105 

6  a.  m. 

-104 

8  a.  m. 

-100 

9  a.  m. 

-  97 

10  a.  m. 

-  97 

11  a.  m. 

-  98 

32  HYDROSTATIC  SYSTEM  OF  TREES. 


Table  4 — Continued. 


Date. 

Time. 

Suction 

or 

pressure 

in 

mm.  Hg. 

Remarks. 

1925 

Aug.  28 

2h  m  p.  m. 

-  96 

4  p.  m. 

-  97 

7  p.  m. 

-  99 

9  p.  m. 

-101 

Aug.  29 

3  a.  m. 

-106 

4  a.  m. 

-104 

6  a.  m. 

-104 

8  a.  m. 

-101 

Aug.  30 

9  a.  m. 

-104 

Fog  and  dew. 

12  m. 

-  97 

Clear. 

6  p.  m. 

-  99 

Aug.  31 

9  a.  m. 

-  98 

4  p.  m. 

-  94 

Sept.  1 

7  a.  m. 

-103 

Rain  clouds. 

9  a.  m. 

. 

Fittings  defective.  U  tube  replaced  by  vertical  column. 

Good  connections  to  bore  not  restored  until  Sept.  21. 

Sept.  21 

4  p.  m. 

-145 

Clear. 

Sept.  22 

7  30  a.  m. 

-148 

Do. 

11  30  a.  m. 

-147 

Do. 

5  30  p.  m. 

-153 

Cloudy. 

Sept.  23 

8  a.  m. 

-163 

Do. 

12  m. 

-162 

Clear  after  9  a.  m. 

4  p.  m. 

-166 

Cloudy. 

Sept.  24 

7  15  a.  m. 

-178 

Overcast. 

11  30  a.  m. 

-178 

Clearing. 

Sept.  24 

4  p.  m. 

-179 

Clouds. 

Sept.  25 

8  a.  m. 

-192 

Clear. 

5  p.  m. 

-194 

Do. 

Sept.  26 

7  15  a.  m. 

-206 

Do. 

11  45  a.  m. 

-212 

Do. 

4  p.  m. 

-214 

Do. 

Sept.  28 

7  30  a.  m. 

-228 

Some  clouds. 

Sept.  29 

9  45  a.  m. 

-242 

Clear  and  cold. 

Sept.  30 

4  p.  m. 

-248 

Do. 

Oct.  4 

9  a.  m. 

-280 

Reset  at  —305  mm. 

4  p.  m. 

-307 

Clear. 

Oct.  5 

7  30  a.  m. 

-312 

Do. 

2  30  p.  m. 

-307 

Clouds. 

Oct.  6 

7  30  a.  m. 

-312 

Clear. 

5  p.  m. 

-305 

Do. 

Oct.  7 

7  45  a.  m. 

-317 

Do. 

12  m. 

-303 

Do. 

3  15  p.  m. 

-308 

Do. 

6  30  p.  m. 

-317 

Do. 

Oct.  8 

7  30  a.  m. 

-322 

Clear  and  cold. 

4  p.  m. 

-313 

Clear. 

Oct.  9 

7  30  a.  m. 

-324 

Cloudy. 

3  30  p.  m. 

-296 

Air  released;  reset  at  —296. 

Oct.  10 

8  a.  m. 

-306 

Cloudy. 

12  m. 

-304 

Do. 

4  p.  m. 

-306 

Do. 

Oct.  11 

8  a.  m. 

-313 

Do. 

Oct.  12 

8  a.  m. 

-324 

Cloudy. 

4  p.  m. 

-320 

Clear. 

Oct.  13 

8  a.  m. 

-320 

Do. 

2  p.  m. 

-322 

Do. 

Oct.  14 

8  a.  m. 

-330 

Do. 

Oct.  16 

9  a.  m. 

-332 

Cloudy. 

4  p.  m. 

-380 

Do. 

Oct.  17 

9  a.  m. 

-333 

Do. 

3  p.  m. 

-330 

Sun;  air  bubble  out;  reset  at  —290. 

Oct.  18 

8  a.  m. 

-302 

Clear. 

Oct.  19 

8  a.  m. 

-305 

Do. 

4  p.  m. 

-288 

Do. 

SUCTION  IN  TRUNKS  OF  MONTEREY  PINE. 


33 


Table  4 — Continued. 


Date. 

Time. 

Suction 

or 

pressure 

in 

mm.  Hg. 

Remarks. 

1925 

Oct.  20 

7h30m  a.  m. 

-295 

Clear. 

2  p.  m. 

-280 

Do 

Oct.  21 

8  a.  m. 

-286 

Do. 

Oct.  22 

4  p.  m. 

-286 

Do. 

Oct.  23 

7  a.  m. 

-295 

Do. 

11  a.  m. 

-288 

Do. 

Oct.  24 

7  a.  m. 

-296 

Do. 

12  m. 

-287 

Do. 

7  p.  m. 

-290 

Do. 

Oct.  25 

8  a.  m. 

-292 

Do. 

Oct.  26 

7  30  a.  m. 

-292 

Do. 

Oct.  27 

8  a.  m. 

-300 

Overcast. 

Oct.  28 

7  30  a.  m. 

-305 

Do. 

4  p.  m. 

-300 

Do. 

Oct.  29 

2  p.  m. 

-300 

Clear. 

Oct.  30 

7  30  a.  m. 

-312 

Overcast. 

8  a.  m. 

-312 

Do. 

Nov.  1 

10  30  a.  m. 

-316 

Do. 

Nov.  2 

8  a.  m. 

-325 

Showers. 

Nov.  3 

9  a.  m. 

-330 

Clearing. 

Nov.  4 

8  a.  m. 

-331 

Do. 

4  p.  m. 

-330 

Clear. 

Nov.  5 

8  a.  m. 

-338 

Do. 

4  p.  m. 

-331 

Do. 

Nov.  6 

8  a.  m. 

-340 

Do. 

3  p.  m. 

-332 

Do. 

Nov.  7 

8  a.  m. 

-340 

Do. 

Nov.  8 

10  a.  m. 

-332 

Do. 

Nov.  9 

8  a.  m. 

-341 

Do. 

3  p.  m. 

-332 

Cloudy. 

Nov.  10 

4  p.  m. 

-337 

Do. 

Nov.  11 

7  30  a.  m. 

-338 

Raining. 

4  p.  m. 

-338 

Do. 

Nov.  12 

8  a.  m. 

-340 

Cloudy. 

4  p.  m. 

-336 

Raining. 

Nov.  13 

7  30  a.  .m 

-345 

Clear;  air  released;  reset  at  —340. 

Nov.  14 

7  30  a.  m. 

-340 

Clear. 

4  p.  m. 

-334 

Do. 

Nov.  15 

8  a.  m. 

-340 

Do. 

1  30  p.  m. 

-331 

Do. 

6  p.  m. 

-338 

Cloudy. 

Nov.  16 

8  a.  m. 

-336 

Drizzle. 

Nov.  17 

7  30  a.  m. 

-341 

Clear. 

Nov.  18 

7  30  a.  m. 

-342 

Clear. 

11  30  a.  m. 

-333 

Do. 

2  p.  m. 

-332 

Do. 

7  p.  m. 

-338 

Do. 

Nov.  19 

7  30  a.  m. 

-340 

Do. 

Nov.  20 

8  a.  m. 

-310 

Clear;  no  air  drawn  out;  leaking. 

The  expected  positive  pressure  was  illustrated  by  the  records  of  the 
first  two  days  when  a  maximum  of  3.2  atmospheres  was  observed. 
Positive  pressure  on  one  day  in  July  was  an  erratic  occurrence  for  which 
no  explanation  can  be  offered.  Variations  in  which  suction  was 
greatest  at  mid-day  were  seen  in  the  earlier  part  of  the  record,  to  be 
followed  by  the  cycle  in  which  it  was  least  at  the  time  of  the  greatest 


34 


HYDROSTATIC  SYSTEM  OF  TREES. 


expansion  of  the  included  gases.  Here,  as  in  other  trees,  when  the 
instrument  was  reset  at  0,  suction  climbed  slowly  to  a  maximum,  which 
was  —345  mm.  Hg.  =  0.45  atmospheres  for  the  season,  near  which 
amount  it  stood  for  some  time.  Mid-day  decreases  did  not  exceed 
15  mm.  Hg.,  but  greater  changes  might  ensue  in  general  increase  of 
suction  in  a  day. 

Something  of  the  nature  of  the  suction  was  disclosed  by  measurements 
of  the  amount  of  water  which  might  be  taken  in  through  the  bore. 

On  August  6  to  10, 6.4  ml.  were  absorbed.  The  higher  initial  rate  may 
be  ascribed  to  combined  action  of  capillarity  and  tension  in  the  water- 
column.  Later,  after  the  capillary  extension  of  the  water  had  reached 
its  limit,  the  rate  indicated  that  of  the  pull  transmitted  from  the  leaves. 

A  sudden  variation  by  which  suction  decreased  from  —292  mm.  Hg. 
to  —50  over  night  on  August  20  may  not  be  attributed  entirely  to 
defective  joints  found  2  days  later,  as  a  second  occurrence  of  this  began 
on  November  20,  and  similar  observations  have  been  made  on  the  oak. 

Records  of  the  variations  in  diameter  of  the  Pinus  radiata ,  No.  6 
(Dendrographic  series),  have  been  made  since  March  1920.  It  is  about 
22  to  24  years  old,  and  has  a  diameter  of  22  cm.  near  the  base.  An 
8-mm.  bore  was  driven  tangentially  in  the  trunk  about  80  cm.  above 
the  base,  to  which  a  manometer  with  a  closed  arm  was  fitted  at  first, 
to  be  replaced  by  other  instruments  later  as  noted.  The  readings  of 
the  first  instrument  give  the  length  of  the  air-column  in  the  closed 
end  under  compression  denoting  exudation  pressure,  and  extension 
denoting  suction  (fig.  9).  The  bore  probably  opened  into  the  central 
cylinder  (fig.  1  D)  and  the  sap-carrying  layer  (fig.  1  B). 


SUCTION  IN  CUT  ENDS  OF  ROOTS  OF  MONTEREY  PINE. 


35 


Fig.  9. — Manometers  attached  to  Monterey  pine  (No.  6  Dendrographic  series).  U  manometer  on 
left  is  attached  to  a  tangential  bore  in  which  pressure  was  measured  April-November  1925. 
Manometer  with  vertical  tube  on  right  is  attached  to  radial  bore  on  wrhich  observations  w'ere 
made  for  a[few  days  only. 


36 


HYDROSTATIC  SYSTEM  OF  TREES 


Table  5. 


Date. 

Time. 

Length  of 
air-column  in  mm. 

Remarks. 

1925 

Apr. 

15 

3h55m 

p.  m. 

80 

4 

p.  m. 

81 

4 

10 

p.  m. 

80 

4 

30 

p.  m. 

78 

Apr. 

16 

8 

a.  m. 

45 

10 

a.  m. 

48 

Apr. 

17 

8 

a.  m. 

43  =1.9  atm. 

10 

30 

a.  m. 

44 

2 

p.  m. 

45 

3 

p.  m. 

67 

Apr. 

18 

3 

p.  m. 

47 

Apr. 

19 

9 

a.  m. 

42 

Apr. 

20 

9 

a.  m. 

45 

Apr. 

21 

9 

a.  m. 

48 

Apr. 

22 

9 

a.  m. 

52 

Apr. 

23 

9 

a.  m. 

54 

Apr. 

24 

9 

a.  m. 

56 

Apr. 

25 

10 

30 

a.  m. 

58 

Apr. 

26 

10 

a.  m. 

61 

Apr. 

27 

10 

a.  m. 

67 

Apr. 

28 

9 

30 

a.  m. 

69 

Apr. 

29 

9 

15 

a.  m. 

73 

Apr. 

30 

9 

30 

a.  m. 

77 

May 

1 

9 

40 

a.  m. 

74 

May 

2 

9 

10 

a.  m. 

81 

May 

3 

10 

15 

a.  m. 

86 

May 

4 

9 

30 

a.  m. 

84 

May 

5 

9 

45 

a.  m. 

82 

May 

6 

9 

10 

a.  m. 

84 

May 

7 

9 

a.  m. 

86 

May 

8 

9 

a.  m. 

87 

May 

9 

9 

10 

a.  m. 

88 

May 

10 

9 

15 

a.  m. 

89 

May 

11 

9 

20 

a.  m. 

89 

May 

14 

2 

a.  m. 

83 

Refitted;  resinous  material  in  liquid  condition. 

May 

15 

8 

a.  m. 

77 

May 

16 

8 

a.  m. 

70 

3 

p.  m. 

73 

May 

17 

8 

a.  m. 

74 

3 

30 

p.  m. 

78 

May 

18 

8 

a.  m. 

80 

No  significant  variation  in  following  37  days,  and 

fittings  became  imperfect.  Bore  cleaned  and 

refitted  with  larger  tube  of  type  shown  in 

July 

2 

9 

a.  m. 

102=0 

fig.  8  C. 

9 

30 

a.  m. 

98 

11 

a.  m. 

80 

Exudation  pressure  =1.26  atm. 

7 

p.  m. 

100 

July 

3 

7 

a.  m. 

112 

8 

30 

a.  m. 

110 

11 

a.  m. 

110 

2 

30 

p.  m. 

112 

5 

p.  m. 

114 

July 

4 

9 

a.  m. 

113 

11 

a.  m. 

113 

3 

30 

p.  m. 

113 

July 

5 

8 

30 

a.  m. 

115 

10 

30 

a.  m. 

115 

Clear. 

4 

30 

p.  m. 

115 

Do. 

July 

6 

7 

a.  m. 

115 

Do. 

11 

a.  m. 

114 

Do. 

6 

30 

p.  m. 

117 

Do. 

SUCTION  IN  TRUNK  OF  MONTEREY  PINE 


37 


Table  5 — Continued. 


Date. 

Time. 

Length  of 
air-column  in  mm. 

Remarks. 

1925 

July  7 

7h  m  a.  m. 

115 

Overcast. 

9  a.  m. 

115 

Do. 

2  p.  m. 

115 

Clear. 

4  p.  m. 

117 

Do. 

July  8 

7  30  a.  m. 

117 

Overcast. 

9  30  a.  m. 

117 

Clearing. 

2  p.  m. 

117 

Clear. 

4  p.  m. 

117 

Overcast. 

July  9 

7  30  a.  m. 

118 

Fog  and  drizzle. 

10  30  a.  m. 

116 

Do. 

4  p.  m. 

117 

Overcast. 

July  11 

7  30  a.  m. 

115 

Clear. 

11  a.  m. 

115 

Do. 

2  30  p.  m. 

115 

Do. 

3  15  p.  m. 

115 

Reset,  after  cleaning  out  bore,  at  102. 

4  30  p.  m. 

106 

July  12 

8  a.  m. 

110 

Clear. 

10  30  a.  m. 

110 

July  13 

7  30  a.  m. 

114 

9  30  a.  m. 

115 

12  m. 

114 

July  14 

7  30  a.  m. 

115 

Clear. 

11  30  a.  m. 

116 

Do. 

2  15  p.  m. 

117 

Do. 

July  15 

7  30  a.  m. 

117 

Foggy. 

9  30  a.  m. 

117 

Clear. 

1  30  p.  m. 

117 

Do. 

July  16 

7  a.  m. 

117 

Do. 

11  a.  m. 

117 

Do. 

3  30  p.  m. 

118 

Do. 

July  17 

7  a.  m. 

118 

Do. 

3  15  p.  m. 

119 

Do. 

July  18 

7  a.  m. 

117 

Do. 

11  30  a.  m. 

118 

Clouds. 

4  p.  m. 

117 

Do. 

July  19 

7  40  a.  m. 

117 

Do. 

10  a.  m. 

115 

Clouds. 

5  p.  m. 

116 

Cloudy. 

July  20 

7  a.  m. 

110 

Do. 

11  30  a.  m. 

114 

Clouds. 

3  30  p.  m. 

112 

Clear.  „ 

July  21 

7  a.  m. 

113 

Overcast. 

11  a.  m. 

112 

Do. 

4  p.  m. 

113 

Clouds  and  sun. 

July  22 

7  a.  m. 

110 

Drizzling. 

4  30  p.  m. 

110 

Overcast. 

July  23 

8  a.  m. 

108 

Do. 

11  45  a.  m. 

108 

Clear. 

4  p.  m. 

113 

Do. 

July  24 

7  30  a.  m. 

108 

Cloudy. 

4  p.  m. 

108 

Clouds  and  sunshine. 

8  p.  m. 

108 

July  25 

7  30  a.  m. 

106 

Overcast. 

9  a.  m. 

108 

Clear. 

12  m. 

108 

Do. 

3  p.  m. 

107 

Clouds. 

July  26 

7  30  a.  m. 

106 

Fog. 

10  a.  m. 

106 

Overcast. 

3  p.  m. 

106 

Do. 

July  27 

7  a.  m. 

11  30  a.  m. 

105 

Do. 

2  30  p.  m. 

105 

Do. 

38 


HYDROSTATIC  SYSTEM  OF  TREES 


Table  5 — Continued. 


Date. 

Time. 

Length  of 
air-column 
in  mm. 

Remarks. 

1925 

July  28 

7h  111  a.  m. 

106 

Overcast. 

11  a.  m. 

105 

Do. 

July  28 

2  p.  m. 

105 

Sunny. 

July  29 

7  40  a.  m. 

106 

Overcast. 

July  30 

8  a.  m. 

105 

Dripping  fog. 

4  p.  m. 

105 

Overcast. 

July  31 

7  30  a.  m. 

106 

Do. 

11  30  a.  m. 

106 

Sun  coming  out. 

Aug.  2 

3  45  p.  m. 

106 

Do. 

Aug.  3 

7  30  a.  m. 

Overcast. 

11  30  a.  m. 

105 

Sunshine. 

3  45  p.  m. 

105 

Do. 

Aug.  4 

8  a.  m. 

105 

Overcast. 

2  30  p.  m. 

105 

Sunny. 

Aug.  5 

9  a.  m. 

107 

Fog. 

Aug.  6 

2  30  p.  m. 

107 

Clear. 

Aug.  7 

9  a.  m. 

105 

Fog. 

4  p.  m. 

106 

Clear. 

Aug.  8 

8  a.  m. 

105 

Fog. 

4  p.  m. 

105 

Aug.  9 

8  30  a.  m. 

104 

Overcast. 

7  p.  m. 

108 

Aug.  10 

8  a.  m. 

105 

Overcast. 

11  a.  m. 

104 

Sunny. 

4  p.  m. 

107 

Air  released;  reset  to  0  103. 

Aug.  11 

8  a.  m. 

104 

Sunny. 

11  30  a.  m. 

106 

Do. 

7  30  p.  m. 

107 

Do. 

Aug.  12 

7  30  a.  m. 

103 

Do. 

11  a.  m. 

103 

Do. 

4  15  p.  m. 

104 

Do. 

Aug.  13 

7  30  a.  m. 

106 

Overcast. 

11  30  a.  m. 

107 

Do. 

7  p.  m. 

108 

Sun  in  afternoon. 

Aug.  14 

5  45  a.  m. 

105 

Overcast. 

8  45  a.  m. 

104 

Clearing. 

Aug.  15 

11  a.  m. 

107 

Overcast. 

Aug.  16 

7  30  a.  m. 

108 

Do. 

4  p.  m. 

109 

Do. 

Aug.  17 

7  30  a.  m. 

109 

Do. 

11  30  a.  m. 

108 

Clear. 

4  p.  m. 

108 

Do. 

Aug.  18 

7  30  a.  m. 

103 

Do. 

11  a.  m. 

102 

Do. 

4  p.  m. 

105 

Do. 

Aug.  19 

7  a.  m. 

105 

• 

11  45  a.  m. 

104 

4  15  p.  m. 

105 

Aug.  20 

7  30  a.  m. 

104 

11  30  a.  m. 

104 

Aug.  21 

3  30  p.  m. 

105 

Fitting  of  tube  to  bore  made  secure  and  closed  mano- 

meter  replaced  by  arrangement  similar  to  fig.  9  B. 

Suction 

in 

mm.  Hg. 

Aug.  22 

3  p.  m. 

. 

• 

5  p.  m. 

-  10 

Aug.  23 

8  a.  m. 

-  22 

Misting. 

11  a.  m. 

-  20 

Clearing. 

SUCTION  IN  TRUNKS  OF  MONTEREY  PINE.  39 


Table  5 — Continued. 


Date. 

Time. 

Suction 

in 

mm.  Hg. 

Remarks. 

1925 

Aug.  23 

4I1  ir 

p.  m. 

-  20 

Clearing. 

Aug.  24 

7  30 

a.  m. 

-  22 

Clear. 

11  30 

a.  m. 

-  18 

Do. 

4 

p.  m. 

-  23 

Do. 

Aug.  25 

7  30 

a.  m. 

-  25 

Warm  and  clear. 

11  30 

a.  m. 

-  22 

Do. 

4 

p.  m. 

-  25 

Do. 

Aug.  26 

8 

a.  m. 

-  25 

Overcast. 

11  30 

a.  m. 

-  27 

Beginning  to  clear. 

7  15 

p.  m. 

-  28 

Overcast. 

Aug.  27 

6 

a.  m. 

-  30 

7 

a.  m. 

-  30 

8 

a.  m. 

-  27 

9 

a.  m. 

-  25 

10 

a.  m. 

-  22 

11 

a.  m. 

-  16 

12 

m. 

-  10 

2 

p.  m. 

-  5 

3 

p.  m. 

-  0 

4 

p.  m. 

-  0 

5 

p.  m. 

-  0 

8 

p.  m. 

-  0 

Aug.  28 

10 

a.  m. 

•  ••••  ••• 

Reset  withjU-tube  manometer. 

11 

a.  m. 

-  6 

2 

a.  m. 

-  8 

4 

a.  m. 

-  8 

7 

a.  m. 

-  11 

9 

a.  m. 

-  13 

Aug.  29 

3 

a.  m. 

-  12 

4 

a.  m. 

-  17 

6 

a.  m. 

-  15 

. 

8 

a.  m. 

-  15 

Aug.  30 

9 

a.  m. 

-  21 

Fog  and  dew. 

12 

m. 

-  20 

Sunny. 

6 

p.  m. 

-  21 

Overcast. 

Aug.  31 

9 

a.  m. 

-  25 

Sunny. 

4 

p.  m. 

-  26 

Do. 

Sept.  1 

7 

a.  m. 

-  32 

Rain-clouds. 

12 

m. 

-  27 

Sunny. 

7 

p.  m. 

-  35 

Clear. 

Sept.  2 

7 

a.  m. 

-  30 

Clearing. 

11 

a.  m. 

-  28 

Clear. 

Sept.  5 

11 

a.  m. 

-  17 

Do. 

6  30 

p.  m. 

-  17 

Do. 

Sept.  6 

8  30 

a.  m. 

-  12 

Clearing  after  shower. 

10 

a.  m. 

•  •••••••• 

Instrument  adjusted  and  set*at  0. 

6 

p.  m. 

-  8 

Clouds. 

Sept.  7 

7  30 

a.  m. 

-  17 

11  15 

a.  m. 

-  13 

Clear. 

4  30 

p.  m. 

-  24 

Do. 

Sept.  8 

7  30 

a.  m. 

-  22 

Do. 

11  30 

a.  m. 

-  25 

Do. 

4 

p.  m. 

-  29 

Do. 

Sept.  9 

8 

a.  m. 

-  36 

Cloudy  since  early  morning. 

11  30 

a.  m. 

-  34 

Clear. 

Sept.  10 

7  30 

a.  m. 

-  35 

Cloudy. 

Sept.  131 

8 

a.  m. 

-  60 

Clearing. 

11 

a.  m. 

•  •••••••• 

6 

p.  m. 

-  62 

Clear. 

1  A  bore  10  mm.  in  diameter  was  driven  radially  into  trunk  at  lower  level  and  fitted  with  a 
tube,  fig.  8  B,  connecting  with  a  vertical  capillary  tube  (see  fig.  9  B).  No  water  was  put  into 
system,  and  resinous  exudate  was  collected  until  Sept.  22,  when  tubes  were  cleaned  and  filled 
with  water  in  usual  manner.  Readings  (page  40)  were  obtained  from  this  radial  bore  for  com¬ 
parison  with  those  from  the  tangential.  Various  defects  were  encountered  so  that  no  records 
of  value  were  obtained  until  Sept.  28. 


40 


HYDROSTATIC  SYSTEM  OF  TREES 


Table  5 — Continued. 


Date. 

Time. 

Suction 

in 

mm.  Hg. 

Remarks. 

Sept.  14 

7  15 

a.  m. 

—  65 

Clear. 

11  30 

a.  m. 

-  62 

Do. 

4 

p.  m. 

-  64 

Do. 

Sept.  15 

7  15 

a.  m. 

-  68 

Do. 

3  30 

p.  m. 

-  57 

Do. 

Sept.  16 

7  30 

a.  m. 

-  73 

Clear;  some  clouds. 

Sept.  18 

7 

a.  m. 

-  84 

Clouds;  rain  on 

17th. 

Sept.  20 

9 

a.  m. 

-  55 

Clear. 

Sept.  21 

7  30 

a.  m. 

-  57 

Do. 

11  30 

a.  m. 

-  50 

Do. 

4 

p.  m. 

-  56 

Do. 

Sept.  22 

7  30 

a.  m. 

-  54 

Do. 

11  30 

a.  m. 

-  50 

Do. 

5  30 

p.  m. 

-  57 

Cloudy  since  5  p.  m. 

Sept.  23 

8 

a.  m. 

-  64 

Cloudy. 

12 

m. 

-  61 

Do. 

4 

p.  m. 

-  63 

Do. 

Suction  in  mm.  Hg. 

Date. 

Time. 

Remarks. 

Tangential. 

Radial. 

Sept.  24 

7  15 

a.  m. 

-  49 

Clearing. 

11  30 

a.  m. 

-  50 

Clouds. 

4 

p.  m. 

-  51 

Clear. 

Sept.  25 

8 

a.  m. 

-  53 

Do. 

5 

p.  m. 

-  54 

Do. 

Sept.  26 

7  15 

a.  m. 

-  61 

Do. 

11  45 

a.  m. 

-  53 

Do. 

4 

p.  m. 

-  56 

Clouds. 

Sept.  28 

7  30 

a.  m. 

-  48 

-10 

Clear. 

Sept.  29 

9  45 

a.  m. 

-  25 

-17 

Do. 

Sept.  30 

4 

p.  m. 

-  38 

-24 

Do. 

Oct.  4 

9 

a.  m. 

-  44 

-42 

Do. 

4 

p.  m. 

-  44 

-42 

Do. 

Oct.  5 

7  30 

a.  m. 

-  47 

-45 

Clouds. 

2  30 

p.  m. 

-  39 

-33 

Clear. 

Oct.  6 

7  30 

a.  m. 

-  47 

-42 

Do. 

5 

p.  m. 

-  44 

-48 

Do. 

Oct.  7 

7  45 

a.  m. 

-  54 

-46 

Do. 

12 

m. 

-  45 

-42 

Do. 

3  15 

p.  m. 

-  45 

-46 

Do. 

6  30 

p.  m. 

-  51 

-51 

Do. 

Oct.  8 

7  30 

a.  m. 

-  66 

-54 

4 

p.  m. 

-  55 

-44 

Do. 

Oct.  9 

7  30 

a.  m. 

-  63 

-54 

Cloudy. 

3  30 

p.  m. 

-  66 

-56 

Do. 

Oct.  10 

8 

a.  m. 

-  66 

-56 

Do. 

12 

m. 

-  66 

-54 

Cloudy. 

4 

p.  m. 

-  67 

-58 

Do. 

Oct.  11 

8 

a.  m. 

-  72 

-63 

Do. 

Oct.  12 

8 

a.  m. 

-  90 

-70 

Raining  since  noon. 

4 

p.  m. 

-  78 

-66 

Oct.  13 

8 

a.  m. 

-  90 

-74 

Clouds  and  sun. 

2 

p.  m. 

-  78 

-66 

Do. 

Oct.  14 

8 

a.  m. 

-  90 

-79 

Clear. 

Oct.  16 

9 

a.  m. 

-  95 

-84 

Cloudy. 

4 

p.  m. 

-  94 

-84 

Do. 

Oct.  17 

9 

a.  m. 

-  96 

-87 

Do. 

Oct.  18 

8 

p.  m. 

-  98 

-90 

Clear. 

Oct.  19 

9 

a.  m. 

-  81 

-90 

4 

p.  m. 

-  68 

Discontinued 

Date. 


1925 
Oct.  20 

Oct.  21 
Oct.  22 
Oct.  23 

Oct.  24 


Oct.  25 
Oct.  26 
Oct.  27 

Oct.  28 

Oct.  29 
Oct.  30 
Oct.  31 
Nov.  1 
Nov.  2 
Nov.  3 
Nov.  4 

Nov.  5 

Nov.  6 

Nov.  7 
Nov.  8 
Nov.  9 

Nov.  10 
Nov.  11 

Nov.  12 

Nov.  13 
Nov.  14 

Nov.  15 

Nov.  15 
Nov.  16 
Nov.  17 
Nov.  18 


Nov.  19 
Nov.  20 


Nov.  21 


Nov.  22 
Nov.  23 
Nov.  24 

Nov.  25 

Nov.  26 
Nov.  27 
Nov.  28 


SUCTION  IN  TRUNK  OF  MONTEREY  PINE.  41 


Table  5 — Continued. 


Time. 

Suction  in 
mm.  Hg. 

Tangential. 

Remarks. 

7h30m 

a.  m. 

-  78 

Clear. 

2 

p.  m. 

-  69 

Do. 

8 

a.  m. 

-  62 

Do. 

4 

p.  m. 

-  68 

Do. 

7 

a.  m. 

-  78 

Do. 

11 

a.  m. 

-  72 

Do. 

7 

p.  m. 

-  68 

Do. 

12 

m. 

-  56 

Do. 

7 

p.  m. 

-  62 

Do. 

8 

a.  m. 

-  42 

Do. 

7  30 

a.  m. 

-  48 

Clear;  air  in  tube. 

8 

a.  m. 

-  43 

Overcast. 

4 

p.  m. 

-  41 

Clear. 

7  30 

a.  m. 

-  42 

Overcast. 

4 

p.  m. 

-  38 

Do. 

2 

p.  m. 

-  30 

Clear. 

7  30 

a.  m. 

-  44 

Overcast. 

8 

a.  m. 

-  43 

Do. 

10  30 

a.  m. 

-  48 

Do. 

8 

a.  m. 

-  56 

Showers. 

9 

a.  m. 

-  60 

Clearing. 

8 

a.  in. 

-  46 

Do. 

4 

p.  m. 

-  50 

Do. 

8 

a.  m. 

-  62 

Clear. 

4 

p.  m. 

-  54 

Do. 

8 

a.  m. 

-  68 

Do. 

3 

p.  m. 

-  60 

Do. 

8 

a.  m. 

-  68 

Do. 

10 

a.  m. 

-  48 

Do. 

8 

a.  m. 

-  68 

Do. 

3 

p.  m. 

-  57 

Cloudy. 

4 

p.  m. 

-  64 

Do. 

7  30 

a.  m. 

-  67 

Raining. 

4 

p.  m. 

-  67 

Do. 

8 

a.  m. 

-  74 

Cloudy. 

4 

p.  m. 

-  68 

Raining. 

7  30 

a.  m. 

-  81 

Clear.  Air  released;  reset  at  —75. 

7  30 

p.  m. 

-  84 

Clear. 

4 

p.  m. 

-  80 

Do. 

8 

a.  m. 

-  54 

Do. 

1  30 

p.  m. 

-  51 

Do. 

4 

p.  m. 

-  56 

Cloudy. 

8 

a.  m. 

-  59 

Drizzle. 

7  30 

a.  m. 

-  68 

Clear. 

7  30 

a.  m. 

-  72 

Do. 

11  30 

a.  m. 

-  66 

Do. 

2 

p.  m. 

-  66 

Do. 

7 

p.  m. 

-  69 

Do. 

7  30 

a.  m. 

-  75 

Do. 

8 

a.  in. 

-  80 

Do. 

11  30 

a.  m. 

-  70 

Do. 

2 

p.  m. 

-  68 

Do. 

4  30 

p.  m. 

-  75 

Do. 

8 

a.  m. 

-  83 

Overcast. 

12 

m. 

-  75 

Slightly  overcast. 

4 

p.  m. 

-  78 

Overcast. 

8 

a.  m. 

-  87 

Clear. 

7  30 

a.  in. 

-  85 

Overcast. 

7  30 

a.  m. 

-  92 

Do. 

2 

p.  m. 

-  90 

Clear. 

7 

a.  in. 

-103 

Do. 

2 

p.  m. 

-  98 

Hazy. 

12 

m. 

-103 

Do. 

8 

a.  m. 

-111 

Clear. 

8 

a.  m. 

-114 

Do. 

42 


HYDROSTATIC  SYSTEM  OF  TREES. 


The  exudation  and  suction  in  this  tree  did  not  reach  the  maxima 
shown  by  No.  28.  Positive  pressures  in  the  tangential  bore  amounting 
to  1.9  atmospheres  were  seen  on  the  second  day  of  the  test,  but  suc¬ 
tion  was  seen  again  in  a  refitted  instrument  nearty  3  months  later. 
Daily  variations  were  as  in  No.  28,  the  mid-day  decrease  not  exceeding 
12  mm.  Hg.  in  any  case.  The  measurements  from  the  radial  bore  were 
indecisive,  and  are  indicative  of  passages  blocked  by  resinous  material. 

Suction  in  these  tests  may  be  attributed  to  the  pull  of  the  leaves  on 
the  continuous  water  column  and  the  maximum  of  90  mm.  Hg.  =0.12 
atmospheres  was  reached  in  October. 

NATURE  OF  EXUDATION  PRESSURE  OF  THE  PINE. 

The  registration  of  comparatively  high  exudation  pressures  in  the 
recently  formed  wood  of  the  Monterey  pine  has  been  previously  de¬ 
scribed.1  Bores  driven  tangentially  in  trees  of  all  ages  which  formed 
heavy  wood-layers  became  the  seat  of  positive  pressures  which  might 
amount  to  as  much  as  4  atmospheres.2 

In  repetition  of  these  experiments,  an  apparatus  consisting  of  a 
threaded  brass  tube  connected  by  heavy  rubber  tubing  with  a  man¬ 
ometer  with  closed  end  and  with  stopcock  and  filling  funnel  was  at¬ 
tached  to  a  tangential  bore  in  Monterey  pine  No.  1  (Dendrographic 
series).  Readings  in  terms  of  the  length  of  the  column  of  air  in  the 
closed  end  of  the  manometer  were  made  (Table  6). 

Another  demonstration  of  exudation  pressure  was  found  by  fixing 
a  section  of  brass  tubing  in  a  shallow  radial  bore  of  a  pine  trunk  12  cm. 
in  diameter  on  June  14,  1923,  and  making  connection  with  an  open 
U  tube  containing  mercury.  The  connecting  tube  and  bore  were 
filled  with  wrater.  The  test  was  begun  at  4  p.  m.  An  hour  later  an 
exudation  pressure  of  12  mm.  Hg.  was  shown.  The  next  morning,  15 
hours  after  beginning,  a  positive  pressure  of  38  mm.  Hg.  was  seen — air 
had  been  forced  out  of  the  wood.  This  was  released  and  the  column 
set  at  0  at  7  a.  m.  At  10  a.  m.  a  positive  pressure  of  16  mm.  Hg. 
had  been  set  up.  The  following  records  were  made  in  continuation  of 
those  given  in  Table  6. 

A  copious  exudation  of  resin  had  taken  place.  Had  a  closed  man¬ 
ometer  been  used,  high  pressures  would  doubtless  have  been  recorded. 

From  these  results  and  those  obtained  from  bores  and  stumps  of 
other  individuals  it  is  seen  that  positive  or  exudation  pressures  are 
exhibited  by  the  pines  only  when  bores  are  driven  into  the  more  re¬ 
cently  formed  wood  and  when  surfaces  are  exposed  from  which  resinous 
material  exudes  copiously.  This  has  also  been  noted  in  a  branch  22 
cm.  in  diameter  in  1924, 3  and  in  1925  by  the  stump  of  a  detached  root 

1  MacDougal,  D.  T.  Reversible  variations  in  volume,  pressure,  and  movements  of  sap  in 
trees.  Pub.  365,  Carnegie  Inst.  Wash.,  1925.  See  pp.  45-58. 

2  MacDougal,  D.  T.  Absorption  and  exudation  pressures  of  sap  in  plants.  Proc.  Amer. 

Phil.  Soc.,  64,  102-130,  1925.  3  Publ.  365,  Carnegie  Inst.  W'ash.,  p.  54,  1925. 


SUCTION  IN  TRUNKS  OF  MONTEREY  PINE. 


43 


as  well  as  on  the  terminus  of  the  larger  part  of  the  root.  In  neither 
of  these  cases  was  the  pressure  more  than  that  of  a  few  mm.  Hg.  when 
measured  in  an  open  manometer.  The  maximum  is  attained  within  2 
days,  then  gradually  declines.  Removal  of  resin  from  the  bore  and 
freshening  the  surfaces  is  followed  by  a  slight  renewal  of  action.  It  is 
only  when  closed  manometers  with  small  bores  are  used  that  high 
pressures  are  developed.  By  the  use  of  short  thin  air-columns  an 
increase  of  1  to  3  ml.  of  material  to  the  contents  of  the  bore  may  set 
up  pressures  of  4  atmospheres  which  soon  decline. 


Table  6. 


Date. 

Time. 

Length  of 
air-column. 

Remarks. 

1925. 

mm. 

Apr.  14 

4h00m  p.  m. 

110 

Borehole  tangential  to  wood  of  1923. 

4  20  p.  m. 

115 

Suction  or  absorption. 

4  30  p.  m. 

103  * 

Do. 

4  35  p.  m. 

93 

Exudation  began. 

Apr.  15 

7  a.  m. 

27 

Pressure  equivalent  to  4  atmospheres. 

9  a.  m. 

27 

12  m. 

24 

2  30  p.  m. 

45 

4  p.  m. 

50 

Apr.  16 

8  a.  m. 

57 

Manometer  disconnected;  leading  tube  filled  with  heavy 

10  a.  m. 

90 

resinous  liquid.  Emptied,  refilled  with  wrater  and  set 

at  112  mm. 

Apr.  17 

8  a.  m. 

82 

Positive  or  exudation  pressure  followed  renewal,  but 

10  30  a.  m. 

82 

this  gradually  lessened  until  the  19th  when  absorption 

2  p.  m. 

85 

began,  which  continued  to  lengthen  air-column  until 

3  p.  m. 

86 

the  21st,  when  this  phase  began  to  wane  and  air 

Apr.  18 

3  p.  m. 

95 

column  was  again  compressed. 

Apr.  19 

9  a.  m. 

106 

Apr.  20 

9  a.  m. 

122 

Apr.  21 

9  a.  m. 

122 

Apr.  22 

9  a.  m. 

107 

Apr.  23 

9  a.  m. 

105 

Apr.  24 

9  a.  m. 

100 

Air-column  w*as  maintained  in  a  compressed  condition 

Apr.  25 

10  30  a.  m. 

99 

with  but  little  variation  for  20  days.  At  end  of  this 

Apr.  26 

10  a.  m. 

100 

time  manometer  was  taken  down.  Metal  tube  and 

Apr.  27 

10  a.  m. 

100 

borehole  were  found  to  be  filled  with  hardened  resin. 

Apr.  28 

9  30  a.  m. 

98 

This  removed,  and  instrument  again  sealed  in  place; 

Apr.  29 

9  15  a.  m. 

99 

set  at  95. 

Apr.  30 

9  30  a.  m. 

99 

May  1 

9  40  a.  m. 

97 

May  13 

5  p.  m. 

95 

May  14 

8  a.  m. 

98 

2  p.  m. 

98 

May  15 

8  a.  m. 

98 

May  16 

8  a.  m. 

98 

The  entire  cycle  of  action  is  coincidental  with  the  exudation  of  resin 
into  the  bores  and  must  be  attributed  mainly  to  this  cause,  the  ulti¬ 
mate  seat  of  energy  being  the  osmotically  active  contents  of  the  living 
cells  which  surround  the  resin  ducts.  To  this  may  be  added  the  initial 
hydration  and  expansion  of  living  cells  of  the  rays  and  their  subsequent 
contraction  by  dehydration  in  a  manner  which  can  be  best  analyzed  by 


44 


HYDROSTATIC  SYSTEM  OF  TREES. 


bores  made  in  thick  layers  of  parenchymatous  cells.  The  results  of 
such  tests1  of  the  action  of  the  thick  succulent  cortex  of  the  tree  cactus, 
Carnegiea  gigantea ,  have  been  recently  described. 

TEST  FOR  “ROOT-PRESSURE”  IN  PINE  TREES. 

The  classic  form  of  demonstration  of  “root-pressure”  is  by  a  man¬ 
ometer  fitted  to  the  stump  of  a  stem  of  a  small  plant.  No  positive 
pressures  of  this  kind  in  the  pines  seems  to  have  been  reported,  although 
slight  positive  pressures  have  been  detected  in  branches  by  various 
authors.  The  experiment  was  repeated  as  shown  in  Table  8. 

No  positive  or  exudation  pressure  was  shown  by  this  stump,  the 
surface  of  which  was  only  a  few  centimeters  above  the  ground.  The 
outflow  of  resin  was  slight,  and  here,  as  elsewhere  in  the  pines,  no 
action  in  the  roots  has  been  found  which  would  force  liquid  upward 
through  the  wood  or  the  elongated  conduits  of  the  protoxylem. 


Table  7. 


Date. 

Time. 

Length  of 
air-column. 

Date. 

Time. 

Length  of 
air-column. 

1925 

mm. 

1925 

mm. 

June  16 

8h30m  a.  m. 

+  100 

June  18 

8h00m  a.  m. 

+  108 

9  30  a.  m. 

+  104 

10  a.  m. 

+  108 

12  30  p.  m. 

+  106 

12  m. 

+  103 

2  30  p.  m. 

+  98 

June  19 

8  a.  m. 

+  95 

June  17 

8  a.  m. 

+  107 

3  p.  m. 

+  95 

9  a.  m. 

+  109 

June  20 

8  a.  m. 

+  90 

11  a.  m. 

+  112 

June  21 

10  a.  m. 

+  80 

3  p.  m. 

+  113 

COMPOSITION  AND  ACTION  OF  GASES  IN  TRUNKS  OF  PINE 

TREES. 

When  a  bore  is  driven  into  the  more  recently  formed  wood  of  the 
Monterey  pine  filled  with  water  and  quickly  connected  with  a  man¬ 
ometer,  it  is  seen  that  absorption  of  water  and  consequent  suction 
takes  place  during  a  brief  period,  generally  not  exceeding  a  half  hour, 
when  exudation  of  resin  begins  and  a  pressure  as  high  as  4  atmospheres 
may  be  developed  within  the  following  30  hours. 

If  the  clogging  resin  which  soon  becomes  granular  is  removed,  the 
bore  cleaned  and  the  instrument  refitted,  suction  appears  and  con¬ 
tinues  indefinitely  in  the  pine.  On  the  other  hand,  if  a  bore  be  made 
into  the  center  of  the  trunk  and  the  exudation  of  resin  blocked  by 
screwing  a  tube  deeply  into  it,  suction  may  be  shown  at  the  beginning 
and  also  continues  indefinitely.  It  is  not  always  possible  to  drive 
bores  in  such  manner  as  to  open  only  into  recently  formed  water-filled 
wood,  or  into  wood  containing  air,  but  the  approximations  included  in 
the  foregoing  experiments  serve  to  demonstrate  prevalent  conditions. 


1  Proc.  Amer.  Phil.  Soc.,  64,  102-130,  1925. 


SUCTION  IN  TRUNKS  OF  MONTEREY  PINE. 


45 


It  is  generally  conceded  that  the  pressure  of  gases  in  the  central 
cylinder  may  be  less  than  atmospheric,  andPappenheim1  concluded  that 
it  may  be  no  more  than  a  fourth  of  an  atmosphere  in  the  conifers.  The 
factors  which  might  affect  pressure  in  the  central  part  of  a  trunk  would 
be  endodermal  action  in  the  roots  forcing  water  into  the  trunk,  tran¬ 
spiration  in  the  leaves,  setting  up  tension  in  the  cohesive  column  in  the 
outer  layers,  and  excessive  loss  by  diffusion  of  gas  from  the  central 
cylinder.  As  to  the  first  factor,  it  can  not  be  shown  that  any  osmotic 
action  in  the  root  takes  place  which  could  force  water  up  through  the 
tracheids  of  the  Monterey  pine. 

Table  8. 


Date. 

Time. 

Suction  in 
mm.  Hg. 

Remarks. 

1925. 

mm. 

Apr.  15 

3h30m  p.  m. 

•  •••••••• 

Small  tree  cut  off  30  cm.  from  base  where  stump  was 

3  38  p.  m. 

-  24 

7  mm.  thick.  No  branches  remained.  Open  man- 

4  10  p.  m. 

-  66 

ometer  attached,  surfaces  being  irrigated  immediately. 

4  30  p.  m. 

-102 

Apr.  16 

8  a.  m. 

-  66 

10  a.  m. 

-  60 

Length 

Date. 

Time. 

of 

Remarks. 

air-column. 

1925. 

Apr.  17 

8h  m  a.  m. 

-  54 

Refitted  to  stump  which  was  trimmed.  Manometer 

9  a.  m. 

-  55 

replaced  by  one  with  larger  bore  and  closed  end.  Air- 

10  30  a.  m. 

82 

column  43  mm. 

2  p.  m. 

65 

Warm  and  sunny. 

3  p.  m. 

75 

Apr.  18 

3  p.  m. 

70 

Apr.  19 

9  a.  m. 

64 

Apr.  20 

9  a.  m. 

43 

Absorption  pressure  ceased  at  this  point  and  readings 

now  showed  no  action  for  next  20  days. 

May  14 

8  a.  m. 

43 

Thin  section  cut  from  surface  and  manometer  refitted. 

2  p.  m. 

48 

May  15 

8  a.  m. 

50 

May  16 

8  a.  m. 

52 

3  p.  m. 

53 

May  17 

8  a.  m. 

57 

3  30  p.  m. 

59 

May  18 

8  a.  m. 

61 

May  19 

2  p.  m. 

59 

Rain  all  night  and  this  day. 

May  20 

8  30  a.  m. 

59 

May  22 

8  a.  m. 

63 

May  24 

10  a.  m. 

51 

May  25 

8  a.  m. 

51 

4  p.  m. 

51 

May  26 

8  a.  m. 

51 

The  pull  from  the  menisci  in  the  walls  of  the  transpiring  cells  of  the 
leaves  sets  up  tensions  under  which  the  new  wood  contracts,  and  these 
layers  show  increased  suction  at  the  same  time.  This  action  appears 
simple,  direct,  and  as  expected.  When  the  variations  in  the  central 
cylinder  are  considered  it  is  seen  that  the  variations  in  suction  are  not 

1  Eine  Methode  zur  Bestimmung  der  Gasspannung  in  Splinte  der  Nadebaume.  Bot. 
Centralb.,  19.  1,  33,  65,  97,  161,  1892. 


46 


HYDROSTATIC  SYSTEM  OF  TREES. 


always  parallel  to  those  in  the  outer  wood.  In  fact  the  anomalies  are  so 
striking  as  to  necessitate  a  thorough  reconsideration  of  the  entire  matter. 

In  the  first  place  the  conclusion  that  the  gases  in  the  central  cylinder 
are  under  greatly  reduced  pressure  at  all  times  is  open  to  suspicion. 
When  empty  bores  of  standing  trees  of  the  Monterey  pine  were  connected 
by  air-filled  tubes  and  as  quickly  as  possible  dipped  in  water,  columns 
of  water  no  greater  than  22  mm.  in  height  were  pulled  up  within  a  day 
or  two. 

It  might  be  objected  that  the  opening  of  a  bore  into  the  wood  would 
allow  pressures  to  be  equalized.  Communication  through  the  tracheids 
is  by  the  way  of  the  minute  perforations  in  the  membranes  closing  the 
pits,  and  the  relief  of  the  pressure  could  not  take  place  very  extensively 
in  the  few  minutes  before  the  apparatus  is  sealed  into  place.  The 
maintenance  of  such  manometers  in  place  for  several  days  should  show 
a  reestablishment  of  the  lessened  pressure,  if  it  occurs.  Repetition 
of  the  test,  as  first  performed  by  Hales  two  centuries  ago  with  dicoty¬ 
ledons,  and  illustrated  by  Pfeffer,1  gave  no  decisive  results  in  the  pines. 
Later  experiments  which  may  not  be  described  here  suggest  that  the 
included  gases  approach  atmospheric  pressures  in  the  pine  most  nearly 
at  the  beginning  of  the  growing  season,  but  the  seasonal  course  of 
variation  is  yet  to  be  determined. 

In  these  and  all  other  tests  of  the  same  kind  care  must  be  taken  to 
make  allowance  for  the  possible  absorption  of  any  gases  present,  es¬ 
pecially  at  high  partial  pressures. 

The  composition  of  the  internal  gases  of  Pinus  No.  6  was  found  by 
analyzing  a  sample  obtained  from  the  bore  in  which  the  above  air- 
pressure  measurement  had  been  made. 

The  cavity  was  first  cleaned,  then  refitted  with  a  brass  tube  screwed 
in  and  securely  sealed,  after  which  a  gas  receiver  with  column  of 
mercury  in  a  pressure  hose  was  attached.  The  filling  bowl  was  set  to  a 
level  to  maintain  a  suction  of  about  300  mm.  Hg.,  as  noted  below: 

Table  9. 

Oct.  12,  4  p.  m.  Gas  receiver  attached;  column  set  at  300  mm.  Hg. 

Oct.  13,  8  a.  m.  About  60  ml.  gas  and  some  liquid  collected. 

Oct.  16,  9  a.  m.  200  ml.  gas  in  receiver,  which  had  been  drawn  out  in  about  90  hours  at 
pressure  of  less  than  0.5  atmospheres.  This  was  taken  for  analysis  and  found  to 
have  the  following  composition  by  two  tests:  CO2:  4.24  p.  ct. ;  4.21  p.  ct.  0:  15.43 
p.  ct. ;  15.41  p.  ct.  N:  80.33  p.  ct. ;  80.38  p.  ct.  Receiver  was  again  attached  at 
4  p.  m.  and  air  forced  out,  after  which  the  suction  column  was  set  at  500  mm.  Hg. 
Oct.  19,  9  a.  m.  About  200  ml.  gas  had  been  drawn  out  in  60  hours,  and  had  invaded  a  sec¬ 
tion  of  rubber  tubing  not  coated  with  shellac  as  all  other  connections  had  been 
treated.  This  w’ould  have  allowed  some  exchange  with  the  atmosphere  which 
would  have  resulted  in  a  lessened  proportion  of  CO2,  as  is  shown  in  the  results  of 
the  analysis.  The  composition  of  this  sample  was  as  below:  CO2:  3.85  p.  ct. ; 
3.80  p.  ct.  O2:  19.99  p.  ct. ;  15.90  p.  ct.  N:  76.16  p.  ct. ;  76.30  p.  ct. 

Among  the  obvious  inferences  it  may  be  said  that,  the  proportion 
of  N  not  being  widely  different  from  that  of  the  atmosphere,  it  would 


1  Physiology  of  Plants.  Trans,  by  A.  J.  Ewart,  1,  201,  1900. 


GASES  IN  TRUNKS  OF  MONTEREY  PINE. 


47 


appear  that  in  the  liberation  of  gases  dissolved  in  the  water  coming  in 
by  the  roots  some  excess  of  C02  would  result.  The  periphery  of  the 
dead  woody  cylinder  is  a  region  in  which  progressive  maturity  of  wood 
and  death  of  ray  cells  would  free  more  of  this  gas,  while  the  respiration 
of  elements  still  alive  would  be  at  the  expense  of  oxygen  withdrawn  from 
this  reservoir,  and  with  some  replacement  by  C02.  The  disproportion 
is  much  more  notable  in  the  walnut  (see  page  102). 

The  high  partial  pressure  of  C02 — over  150  times  as  great  as  in  the 
atmosphere — is  conclusive  evidence  that  no  direct  connection  exists 
between  the  central  cylinder  and  the  atmosphere,  and  further  that  the 
water-filled  wood  cells,  cambium  and  phloem  constitute  a  complex 
membrane  through  which  *this  gas  diffuses  much  less  readily  than  it 
comes  into  the  central  cylinder  of  the  trunk. 


M.  M.  M.  M.  M.  M.  M.  M. 


Fig.  10. — Dendrograph  record  of  Monterey  pine  No.  6  for  weeks  beginning  June  1,  July  13, 
August  24,  and  October  12,  1925.  First  week  characterized  by  a  high  rate  of  increase 
in  diameter  of  trunk,  with  minimum  daily  contraction  of  the  trunk.  Week  beginning 
July  13  was  notable  for  great  range  of  daily  variation,  during  which  period  variations 
in  suction  were  very  small.  Reversible  variations  were  less  in  wreek  beginning  August 
24,  suction  varying  from  —18  to  —30  mm.  Hg.  Growth  was  nearing  the  end.  The 
week  beginning  October  12  was  characterized  by  reversible  variations  of  slight  extent 
with  gradual  transition  from  expansion  to  contraction.  Suction  was  at  a  maximum 
and  varied  from  —78  to  —90  mm.  Hg.  Growth  had  ceased. 

The  common  practice  of  bathing  cut  surfaces  of  stems,  and  of 
filling  bores  with  water  in  arrangements  for  measuring  pressures, 
initiates  some  disturbances  not  usually  taken  into  account.  Theoreti¬ 
cally,  air  would  be  drawn  into  the  ends  of  the  wood  in  which  the  mesh- 
work  column  of  water  under  tension  exists,  when  this  is  cut  into. 
Water  applied  to  the  surface  would  lessen  the  entrance  of  air  or  prevent 
it  entirely.  At  the  same  time  application  of  water  to  the  surface  of 
older  wood  in  which  a  pressure  less  than  atmospheric  prevails  would 
result  in  some  liquid  being  drawn  into  the  wood,  thus  setting  up  con¬ 
ditions  not  present  in  the  intact  trunk.  Still  further,  water  would 
enter  tubes  and  conduits  or  the  tracheids  by  capillarity  to  an  extent 
determined  chiefly  by  the  size  of  the  openings.  The  attachment  of  a 
manometer  to  a  stump  or  to  a  bore  of  a  pine  tree  would  entail  a 
capillary  movement  of  water  into  the  wood  in  such  manner  that  suction 
not  previously  existent  would  be  registered.  Such  action  would  be 
heightened  by  the  solution  of  some  of  the  gases  present  in  the  entrant 
liquid. 


48 


HYDROSTATIC  SYSTEM  OF  TREES. 


SUCTION  AND  PRESSURE  IN  RADIAL  AND  TANGENTIAL 

BORES— MONTEREY  PINE. 

Preliminary  to  the  extensive  observations  recorded  in  the  preceding 
pages,  closed  manometers,  of  the  type  illustrated  in  figure  2,  were  used 
in  making  tests  between  pressures  in  tangential  and  radial  bores  driven 
in  a  small  standing  pine  tree,  which  had  an  attenuated  trunk  with  thin 
layers  and  a  diameter  of  15  cm.  a  meter  from  the  base. 

The  first  pair  was  installed  May  15,  1925,  and  showed  readings  of 
the  manometer  connected  radially  of  an  increase  in  the  air-column  of  a 
closed  manometer  from  88  to  91  mm.,  a  compression  to  86  mm.  on  the 
next  day,  while  on  the  third  and  fourth  days  the  column  was  drawn  out 
to  92  to  95  mm.  Absorption  was  in  evidence  during  most  of  the  period 
in  question.  The  manometer  connected  with  a  tangential  bore-hole 
showed  absorption  which  extended  the  air-column  from  80  to  96  mm. 
within  3  hours,  a  compression  to  62  mm.  on  the  following  day,  then 
extension  for  2  days.  Both  extension  and  compression  were  more 
marked  in  the  tangential  than  in  the  radial  bore-hole.  The  instru¬ 
ments  reset  in  a  new  pair  of  holes  on  May  21  showed  only  absorption  of 
water  or  suction. 

The  instruments  were  now  refitted  to  new  holes  which  extended 
through  the  trunk,  which  were  closed  at  the  farther  end  by  screw  plugs 
securely  sealed.  The  radial  cavity  showed  an  exudation  pressure 
which  compressed  an  air-column  from  112  mm.  to  107  mm.  7  hours 
later;  absorption  followed,  extending  the  air-column  from  112  to  120 
mm.  The  tangential  cavity  showed  absorption  initially,  by  which  an 
air-column  of  93  mm.  was  extended  to  110  mm.  in  3  hours,  then 
exudation  by  which  it  was  compressed  to  65  =  1.4  atm.  on  the  following 
day. 

The  tree  was  now  cut  down,  a  basal  section  sawed  off,  and  the  newly 
exposed  basal  surface  of  the  trunk  coated  with  a  layer  of  Canada 
balsam  in  cedar  oil.  A  hole  8  mm.  in  diameter  was  bored  longitudinally, 
centered  in  the  3  outer  layers  to  a  length  of  10  cm.,  into  which  a  brass 
tube  was  screwed,  sealed  and  connected  with  a  manometer  with  closed 
end.  The  4  outer  layers  had  a  total  thickness  of  about  16  mm.,  and 
the  cavity  did  not  cut  the  outermost.  A  similar  fitting  was  made  in 
the  center  of  the  trunk. 

Both  connecting  tubes  were  filled  with  a  fuchsin  solution.  The 
outer  layers  gave  immediate  and  rapid  absorption  when  set  up  at 
9.15  a.  m.,  but  air  was  soon  drawn  out  of  the  wood.  When  reset  at 
9.25  a.  m.  the  column  of  air  in  the  closed  end  of  the  manometer  was 
extended  from  102  to  112  mm.  in  5  minutes.  At  the  end  of  15  minutes 
the  column  was  extended  to  123  mm.,  at  which  point  it  was  nearly 
stationary  at  the  end  of  30  minutes. 

The  column  of  air  of  the  instrument  connected  with  the  center  of  the 
trunk,  96  mm.  in  length  originally,  was  extended  slowly,  no  air  was 


SUCTION  AND  PRESSURE  IN  RADIAL  AND  TANGENTIAL  BORES.  49 


drawn  out  of  the  wood,  and  at  the  end  of  15  minutes  the  column  was  101, 
where  it  remained  nearly  stationary. 

At  10.30  a.  m.,  the  column  connected  with  the  center  of  the  trunk  was 
stationary  as  above.  The  column  connected  with  the  outer  layer  was 
extended  to  116  mm.  and  some  air  had  been  drawn  into  the  system. 
When  this  was  removed  and  the  column  set  at  0,  immediate  extension 
of  the  column  indicated  a  continuing  absorption. 

At  3.30  p.  m.  the  center  column  was  unchanged.  It  was  reset  to 
96.  Some  air  had  been  drawn  out  of  the  outer  wood  into  the  leading 
tube  of  the  manometer  attached,  the  pressure  column  being  extended 
from  102  to  110  mm.  The  instrument  being  cleared  and  reset  to  0, 
the  pressure  column  was  extended  from  102  to  118  mm.  in  10  minutes. 
The  column  in  the  instrument  attached  to  the  center  of  the  trunk  was 
extended  from  96  to  103  mm.  in  the  same  time. 

Suction  or  absorption  in  the  outer  layers  of  wood  was  seen  to  draw 
air  from  the  wood  at  0.2  atmosphere.  Suction  in  the  central  part  of 
the  trunk  did  not  exceed  0.05  atmosphere,  and  no  air  was  drawn  out 
of  the  wood.  The  outer  column  was  again  extended  to  118  and  the 
center  one  to  108  mm.  in  15  minutes. 

On  the  following  morning,  and  24  hours  after  the  tests  had  been 
begun,  the  column  of  the  centrally  connected  manometer  had  been 
extended  from  96  to  105  mm.,  and  no  air  had  been  drawn  in.  Gas 
had  been  drawn  into  the  leading  tube  of  the  manometer  connected 
with  the  cavity  in  the  outer  wood  to  an  amount  occupying  the  greater 
part  of  the  space  from  which  about  10  ml.  water  had  been  absorbed. 
This  gas  was  released  (7  a.  m.),  and  the  column  set  to  0.  Immediate 
absorption  caused  the  extension  of  the  air  column  from  102  to  107  mm. 
in  10  minutes.  An  hour  later  (8.20  a.  m.)  the  air  column  was  115  mm. 
in  length,  and  a  large  bubble  (2  ml.)  had  been  drawn  in.  This  was 
released  and  the  column  set  to  0.  The  column  connected  with  the 
center  had  been  extended  to  110,  in  this  interval.  Immediate  absorp¬ 
tion  showed  in  the  outer  layer,  so  that  the  column  was  extended  from 
102  to  110  mm.  in  10  minutes.  The  pressure  stood  at  this  point 
and  was  equivalent  to  nearly  0.08  atmosphere,  and  at  the  end  of  a 
half-hour  a  bubble  of  gas  had  been  drawn  into  the  leading  tube. 
The  column  was  reset  to  0  at  8.45  a.  m.  A  repetition  was  noted  by 
10.10  a.  m.,  at  which  time  similar  action  was  noted  in  a  manometer 
fitted  to  the  opposite  side  of  the  trunk.  Similar  observation  was  made 
at  11  a.  m.,  at  which  time  the  central  bore  had  drawn  the  air-column 
in  the  manometer  from  96  to  112  mm.  with  no  air  in  the  system.  A 
day  later  the  centrally  connected  column  extended  from  96  to  118  mm. 
=  0.23  atmosphere.  The  exudation  of  resin  into  bores  in  the  standing 
tree  was  sufficient  to  cause  some  positive  or  exudation  pressure  in 
both  radially  and  tangentially  driven  cavities  in  the  early  part  of  the 
tests;  later  suction  pressures  appeared. 


50 


HYDROSTATIC  SYSTEM  OF  TREES. 


Fig.  11. — Gas  receiver  D.  A,  in  position,  attached  by  section  of  rubber  pressure  tubing  to  metal 
tube  screwed  into  radial  bore  of  oak  tree.  Column  of  mercury  from  bulb,  B,  is  extended 
through  long  section  of  pressure  tubing  to  fill  receiver  and  tubes  completely.  Gases  originally 
present  are  forced  out  of  upper  end  of  receiver,  after  which  bulb,  B,  is  placed  at  level  which 
will  give  suction  desired.  All  rubber  tubing  into  which  gas  may  be  drawn  is  heavily  coated 
with  shellac. 


TESTS  OF  STUMP  AND  BORES  OF  PINE  TREE. 


51 


The  most  interesting  phase  of  these  results,  however,  is  that  of  the 
suction  exerted  by  the  different  layers  after  the  trunk  had  been  cut  off. 
Tubes  screwed  into  the  sealed  base  of  the  trunk,  one  thus  connecting 
longitudinally  with  the  water-column  in  the  outer  layers,  and  the 
other  with  the  central  old  wood,  gave  opportunities  for  comparing 
the  suction  in  the  two  regions.  It  was  seen  that  water  was  taken  in 
at  a  lower  rate  and  conducted  to  a  much  smaller  distance  in  the  inner 
wood  than  in  the  recently  formed  outer  layers.  It  was  to  be  expected 
that  the  pull  from  the  leaves  would  cause  greater  suction  in  the  outer 
layers.  The  continued  extraction  of  gas  from  these  layers  at  0.2 
atmosphere  proved  the  presence  of  some  air-filled  tracheids  in  the 
4  outer  layers. 

EXTENDED  TESTS  OF  STUMP  AND  BORES  OF  A  SINGLE 

PINE  TREE. 

The  foregoing  series  of  measurements  was  made  on  several  trees. 
It  was  important  to  carry  out  some  tests  with  manometers  connected 
with  different  parts  or  combinations  of  the  hydrostatic  system  of  a 
single  tree  and  to  follow  the  resultant  changes  in  suction  or  pressure 
through  an  extended  period.  Instruments  were  therefore  attached 
to  a  small  tree  (No.  XV),  10  meters  in  height  and  20  cm.  in  diameter 
at  the  base  as  follows  (fig.  12B) :  Tangential  bore  80  cm.  from  base 
of  tree,  4  cm.  in  depth,  into  which  a  tube  of  the  type  shown  in  figure 
8  C  was  screwed  about  2  cm. ;  A,  radial  bore  driven  12  cm.  through  the 
center  of  the  trunk  35  cm.  from  its  base  into  which  a  tube  of  the  type 
of  tube  of  figure  8  B  was  screwed  3  cm. ;  D,  radial  bore  80  cm.  from 
the  base,  3  cm.  in  depth  into  which  a  tube  of  the  type  figure  8  C  was 
driven  2  cm. ;  and  C,  a  section  of  pressure  tubing  was  clamped  to  the 
stump  of  a  branch  110  cm.  from  the  base  of  the  trunk.  The  tangential 
bore  B  probably  connected,  to  some  extent,  with  the  central  cylinder 
of  air-filled  wood;  D  was  intended  to  penetrate  its  outer  part;  and  the 
deep  bore  A  undoubtedly  gave  free  and  full  connection  with  it.  C  was 
connected  with  the  air-filled  wood  through  the  protoxylem  and  central 
wood  and  with  the  outer  solution  carrying  recently  formed  layers. 
It  is  probable  that  the  cortex  and  bark  were  so  compressed  as  to  cut 
off  direct  communication  with  the  water  in  the  leading  tube  of  the 
manometer.  Closed  manometers  were  first  used,  to  be  replaced 
later  by  the  type  shown  in  figure  1 1 .  Observations  made  in  the  August- 
November  period  are  given  in  Table  10. 


52 


HYDROSTATIC  SYSTEM  OF  TREES 


Table  10. 


Date. 

Time. 

Tan¬ 

gential. 

Radial. 

Stump  of  branch. 

Remarks. 

Deep. 

Shallow. 

(Figure 

s  indica 

Lte  suctior 

i  in  mm.  Hg.) 

1925 

Water  absorbed: 

Aug.  15 

3h00m  p.  m. 

115 

115 

Water  was  absorbed 

4  p.  m. 

134 

115 

in  such  quantity 

5  45  p.  m. 

120 

110 

by  the  stub  of  the 

Aug.  16 

8  45  a.  m. 

108  =0 

branch  that  the 

9  a.  m. 

98 

80 

130 

instrument  was 

10  40  a.  m. 

96 

78 

116 

opened  to  allow 

4  p.  m. 

98 

80 

125 

calibration  of 

Aug.  17 

7  30  a.  m. 

100 

85 

amount  taken  in. 

11  30  a.  m. 

100 

87 

110 

Much  air  was 

4  p.  m. 

103 

87 

115 

drawn  out  from 

Aug.  18 

7  30  a.  m. 

104 

93 

115 

the  shallow  radial 

11  a.  m. 

105 

95 

114 

bore. 

4  p.  m. 

105 

94 

116 

Aug.  19 

7  a.  m. 

106 

97 

117 

11  45  a.  m. 

105 

97 

115 

4  ml.  in  5  hrs . 

4  15  p.  m. 

107 

97 

117 

13  ml.  in  4.5  hrs. .  . 

Aug.  20 

7  30  a.  m. 

108 

107 

114 

24  ml.  in  1 1  hours . 

11  30  a.  m. 

109 

108 

114 

7  ml.  in  4  hrs . 

Aug.  21 

3  30  p.  m. 

108 

100 

113 

55  ml.  in  28  hrs. .  .  . 

Aug.  22 

8  a.  m. 

110 

101 

114 

18  ml.  in  16.5  hrs. .  . 

11  30  a.  m. 

108 

101 

113 

5  ml.  in  3.5  hrs . 

107 1 

113 1 

107 

5  p.  m. 

113 

116 

107 

Filled  with  water. 

Cleaned  and  reset 

(Figures  indicate  length  of  air  column  in  closed  end  of  manometer.) 

at  122. 

Aug.  23 

8  a.  m. 

107 

122 

105 

14  ml.  in  15  hrs. .  . 

11  15  a.  m. 

108 

122 

110 

3  ml.  in  3  hrs . 

4  30  p.  m. 

110 

122 

117 

7  ml.  in  4.75  hrs. .  . 

Aug.  24 

7  30  a.  m. 

112 

125 

124 

8  ml.  in  15  hrs. .  .  . 

11  30  a.  m. 

109 

127 

123 

7  ml.  in  8.5  hrs. . .  . 

4  p.  m. 

109 

127 

123 

Aug.  25 

7  30  a.  m. 

113 

115 

127 

11  30  a.  m. 

111 

114 

127 

2.5  ml.  in  4  hrs. .  .  . 

4  p.  m. 

113 

130 

135 

2  ml.  in . 

Aug.  26 

8  a.  m. 

115 

130 

139 

3  ml.  in  16  hrs . 

11  30  a.  m. 

113 

131 

136 

0.5  ml.  in  3.5  hrs. . 

7  15  p.  m. 

116 

131 

139 

1.5  ml.  in  7.75  hrs. 

Suction  in  mm.  Hg. 

Aug.  27 

6  a.  m. 

116 

114 

138 

137 . 

See  record  of  No.  28 

for  environmental 

7  a.  m. 

116 

130 

138 

137 . 

conditions. 

8  a.  m. 

115 

130 

137 

136 . 

9  a.  m. 

115 

131 

139 

138 . 

10  a.  m. 

114 

132 

137 

136 . 

11  a.  m. 

114 

131 

136 

137 . 

12  m. 

114 

130 

136 

139 . 

2  p.  m. 

115 

130 

137 

142 . 

3  p.  m. 

115 

131 

137 

143 . 

4  p.  m. 

115 

130 

137 

Reset  with  open 

manometers  as 

I  igures  in 

mm.  Hg. 

Absorbed. 

shown  in  fig.  11. 

5  p.  m. 

-2 

-  6 

—  8.  350  ml.  by 

stump  in  6  days. 

8  p.  m. 

-5 

-0 

-13 

-20 . 

11  p.  m. 

-8 

-0 

-24 

-42 . 

Aug.  28 

3  a.  m. 

-8 

-1 

-32 

-70 . 

4  a.  m. 

-9 

-2 

-34 

-80 . 

TESTS  OF  STUMP  AND  BORES  OF  PINE  TREE 


53 


Table  10 — Continued. 


Date. 

Time. 

Tan¬ 

gential. 

Radial. 

Stump. 

Remarks. 

Deep. 

Shallow. 

(Figui 

•es  indies 

ite  suctio 

n  in  mm 

•  Hg.) 

1925 

Aug.  28 

6h00m 

a.  m. 

-  9 

-  0 

-  36 

-  85 

8 

a.  m. 

-  9 

-  0 

-  36 

-  89 

9 

a.  m. 

-  8 

-  1 

-  36 

-  90 

10 

a.  m. 

-  9 

-  1 

-  35 

-  86 

11 

a.  m. 

-  8 

-  1 

-  36 

-  84 

2 

p.  m. 

-  9 

-  1 

-  39 

-  84 

4 

p.  m. 

-  10 

Reset. 

-  43 

-  96 

7 

p.  m. 

-  12 

-  12 

-  50 

-  15 

9 

p.  m. 

-  15 

-  19 

-  54 

-  13 

Aug.  29 

3 

a.  m. 

—  15 

-  30 

-  66 

-  12 

4 

a.  m. 

—  15 

-  33 

-  64 

-  14 

6 

a.  m. 

-  15 

-  34 

-  64 

-  12 

. 

8 

a.  m. 

-  16 

-  35 

-  66 

-  12 

Aug.  30 

9 

a.  m. 

-  18 

-  66 

-  78 

-  13 

Air  released  from  stump  and  re- 

set  to  0. 

Aug.  31 

9 

a.  m. 

-  74 

-  86 

-  83 

-  72 

4 

p.  m. 

-  24 

-  81 

-  86 

-  70 

Sept.  1 

7 

a.  m. 

-  32 

-  92 

-  95 

-  13 

12 

m. 

-  38 

-  96 

-  90 

-  5 

7 

p.  m. 

-  42 

-108 

-103 

-  80 

Sept.  2 

7 

a.  m. 

-  57 

-102 

-  90 

-  73 

11 

a.  m. 

-  42 

-109 

-101 

-  41 

Sept.  5 

11 

a.  m. 

—  50 

-122 

-123 

-  72 

6 

30 

p.  m. 

-  56 

-126 

-134 

-108 

Sept.  6 

8 

30 

a.  m. 

-  62 

-129 

-138 

-139 

6 

p.  m. 

-  62 

-116 

-129 

-116 

Air  released  from  stump;  reset 

at  -116. 

Sept.  7 

7 

30 

a.  m. 

-  68 

-135 

-135 

-134 

11 

15 

a.  m. 

-  66 

-134 

-135 

-  81 

4 

30 

p.  m. 

-  67 

-106 

-108 

-138 

Sept.  8 

7 

30 

a.  m. 

-  72 

-146 

-134 

-130 

11 

30 

a.  m. 

-  69 

-140 

-120 

-  84 

Reset  at  84  after  release  of  air. 

4 

p.  m. 

-  72 

-132 

-  91 

-130 

Sept.  9 

8 

a.  m. 

-  76 

-135 

-135 

-122 

11 

30 

a.  m. 

-  73 

-132 

-115 

-  98 

Sept.  10 

7 

30 

a.  m. 

-  67 

-141 

-129 

-129 

Sept.  13 

8 

a.  m. 

-  90 

-120 

-102 

-120 

Air  released;  reset  at  —120. 

6 

p.  m. 

-  93 

-  0 

-  88 

-122 

Refitted. 

Sept.  14 

7 

15 

a.  m. 

-  96 

-  18 

-100 

-130 

11 

30 

a.  m. 

-  92 

-  3 

-  90 

-  81 

4 

p.  m. 

-  93 

-  3 

-  92 

-108 

Sept.  15 

7 

15 

a.  m. 

-  98 

-  18 

-102 

-120 

3 

30 

p.  m. 

-  93 

-  0 

-  96 

-  92 

Reset  at  —84  after  release  of  air. 

Sept.  10 

7 

30 

a.  m. 

-100 

-  14 

-111 

-116 

Sept.  18 

7 

a.  m. 

-108 

-  26 

-141 

-108 

Sept.  20 

9 

a.  m. 

-110 

-  22 

-141 

-  96 

Air  released;  reset  at  —96. 

Sept.  21 

7 

30 

a.  m. 

-102 

-  28 

-148 

-  78 

11 

30 

a.  m. 

-  95 

-  10 

-136 

-  20 

4 

p.  m. 

-  97 

-  12 

-151 

-  66 

Sept.  22 

7 

30 

a.  m. 

-104 

-  26 

-146 

-  57 

11 

30 

a.  m. 

-100 

-  13 

-139 

-  24 

5 

30 

p.  m. 

-102 

-  15 

-136 

-  56 

Sept.  23 

8 

a.  m. 

-108 

-  29 

-148 

-  72 

12 

m. 

-106 

-  22 

-152 

-  42 

4 

p.  m. 

-107 

-  16 

-146 

-  50 

Sept.  24 

7 

15 

a.  m. 

-111 

-  30 

-146 

-  70 

11 

30 

a.  m. 

-111 

-  21 

-125 

-  42 

4 

p.  m. 

-111 

-  20 

-152 

-  50 

Sept.  25 

8 

a.  m. 

-115 

-  29 

-144 

-  60 

5 

p.  m. 

-114 

-  18 

-153 

-  51 

54 


HYDROSTATIC  SYSTEM  OF  TREES 


Table  10 — Continued. 


Date. 

Time. 

Tan¬ 

gential. 

Radial. 

Stump. 

Remarks. 

Deep. 

Shallow. 

(Figur 

es  indica 

ite  suctic 

>n  in  mm 

.  Hg.) 

1925 

Sept.  26 

7h15m 

a.  m. 

-120 

-  33 

-146 

-  68 

11 

45 

a.  m. 

-114 

-  18 

-130 

-  21 

4 

p.  m. 

-  97 

-  17 

-135 

-  45 

Sept.  28 

7 

30 

a.  m. 

-122 

-  27 

-146 

-  68 

Sept.  29 

9 

45 

a.  m. 

-126 

-  36 

-151 

-  84 

Sept.  30 

4 

p.  m. 

-106 

-  17 

-132 

-  65 

Air  released;  reset  at  0. 

Oct.  4 

9 

a.  m. 

-124 

-  34 

-  60 

-  60 

4 

p.  m. 

-135 

-  24 

-  65 

-  57 

Oct.  5 

7 

30 

a.  m. 

-130 

-  36 

-  76 

-  60 

2 

30 

p.  m. 

-126 

-  24 

-  71 

-  42 

Oct.  6 

7 

30 

a.  m. 

-134 

-  40 

-  87 

-  84 

5 

p.  m. 

-132 

-  26 

-  83 

-  63 

Oct.  7 

7 

45 

a.  m. 

-136 

-  44 

-  96 

-  91 

12 

m. 

-128 

-  26 

-  84 

-  55 

3 

15 

p.  m. 

-132 

-  24 

-  88 

-  63 

6 

30 

p.  m. 

-135 

-  30 

-  92 

-  82 

Oct.  8 

7 

30 

a.  m. 

-140 

-  43 

-107 

-100 

4 

p.  m. 

-134 

-  25 

-  96 

-  75 

Oct.  9 

7 

30 

a.  m. 

-140 

-  37 

-108 

-  96 

3 

30 

p.  m. 

-139 

-  32 

-105 

-  81 

Oct.  10 

8 

a.  m. 

-143 

-  31 

-111 

-  94 

12 

m. 

-135 

-  27 

-108 

-  80 

4 

p.  m. 

-141 

-  24 

-113 

-  84 

Oct.  11 

8 

a.  m. 

-144 

-  30 

-120 

-  96 

Oct.  12 

8 

a.  m. 

-153 

-  44 

-130 

-108 

4 

p.  m. 

-150 

-  27 

-126 

-  86 

Oct.  13 

8 

a.  m. 

-156 

-  48 

-137 

-114 

2 

p.  m. 

-150 

-  34 

-126 

-  84 

Oct.  14 

8 

a.  m. 

-157 

-  48 

-152 

-no 

Oct.  16 

9 

a.  m. 

-162 

-  42 

-144 

-106 

4 

p.  m. 

-139 

-  36 

-139 

-  98 

Oct.  17 

8 

a.  m. 

-152 

-  41 

-146 

-107 

Oct.  18 

8 

a.  m. 

-166 

-  51 

-144 

-114 

Oct.  19 

8 

a.  m. 

-130 

-  49 

-144 

-115 

4 

p.  m. 

-140 

-  29 

-130 

-  80 

Oct.  20 

7 

30 

a.  m. 

-168 

-  43 

-146 

-114 

2 

p.  m. 

-162 

-  29 

-142 

-  83 

Oct.  21 

8 

a.  m. 

-168 

-  42 

-146 

-111 

Oct.  22 

4 

p.  m. 

-168 

-  36 

-138 

-  99 

Oct.  23 

7 

a.  m. 

-134 

-  42 

-136 

-120 

11 

a.  m. 

-170 

-  36 

Taken 

-102 

out 

Oct.  24 

7 

a.  m. 

-178 

-  52 

-127 

12 

m. 

-172 

-  39 

-  95 

7 

p.  m. 

-174 

-  38 

-104 

Oct.  25 

8 

a.  m. 

-176 

-  48 

-110 

Oct.  26 

7 

30 

a.  m. 

-174 

-  44 

-116 

Oct.  27 

8 

a.  m. 

-179 

-  51 

-126 

Manometer  replaced  by  gas  re- 

ceiver  and  suction  column. 

4 

p.  m. 

-136 

-  38 

-111 

Oct.  28 

7 

30 

a.  m. 

-183 

-  54 

-123 

4 

p.  m. 

-180 

-  45 

-108 

Oct.  29 

2 

p.  m. 

-180 

-  43 

-102 

Oct.  30 

7 

30 

a.  m. 

-186 

-  54 

-122 

Oct.  31 

8 

a.  m. 

-186 

-  49 

-114 

Overcast. 

Nov.  1 

10 

30 

a.  m. 

-182 

-  40 

-108 

Do. 

Nov.  2 

8 

a.  m. 

-179 

-  54 

-111 

Showers. 

Nov.  3 

9 

a.  m. 

-132 

-  64 

-136 

Clearing. 

Nov.  4 

8 

a.  m. 

-130 

-  65 

-122 

Do. 

11 

a.  m. 

-125 

-  62 

-125 

Clear. 

4 

p.  m. 

-122 

-  59 

-122 

Do. 

TESTS  OF  STUMP  AND  BORES  OF  PINE  TREE. 


55 


Table  10 — Continued. 


Date. 

Time. 

1925 

Nov.  5 

8h  m  a. 

4  p. 

Nov.  6 

8  a. 

3  p. 

Nov.  7 

8  a. 

Nov.  8 

10  a. 

Nov.  9 

8  a. 

3  p. 

Nov.  10 

4  p. 

Nov.  11 

7  30  a. 

4  p. 

Nov.  12 

8  a. 

4  p. 

Nov.  13 

7  30  a. 

Nov.  14 

7  a. 

4  p. 

Nov.  15 

8  a. 

1  30  p. 

4  p. 

Nov.  16 

8  a. 

Nov.  17 

7  30  a. 

Nov.  18 

7  30  a. 

11  30  a. 

2  p. 

7  p. 

Nov.  19 

7  30  a. 

Nov.  20 

8  a. 

11  30  a. 

2  p. 

4  30  p. 

Nov.  21 

8  a. 

12  m. 

4  p. 

Nov.  22 

8  a. 

Nov.  23 

7  30  a. 

Nov.  24 

7  30  a. 

2  p. 

Nov.  25 

7  a. 

2  p. 

Nov.  26 

12  m. 

Nov.  27 

8  a. 

Nov.  28 

8  a. 

Tan¬ 

gential. 

Radial. 

Stump. 

Remarks. 

Deep. 

Shallow. 

(Figui 

~es  indict 

ite  suctic 

>n  in  mm 

•  Hg.) 

m. 

-134 

— 

80 

-123 

Clear. 

m. 

-138 

— 

56 

-102 

Do. 

m. 

-138 

— 

81 

-138 

Do. 

m. 

-129 

— 

67 

-  96 

Do. 

m. 

-138 

— 

81 

-124 

Do. 

m. 

-134 

— 

68 

-  98 

Do. 

m. 

-144 

— 

78 

-135 

Do. 

m. 

-137 

— 

61 

-  92 

Cloudy. 

m. 

-138 

— 

60 

-  96 

Do. 

m. 

-144 

— 

60 

-101 

Raining. 

m. 

-142 

— 

57 

-  96 

Do. 

m. 

-143 

— 

68 

-118 

Cloudy. 

m. 

-144 

— 

60 

-  98 

Raining. 

m. 

-162 

— 

78 

-127 

Clear. 

m. 

-157 

— 

84 

-140 

Do. 

m. 

-147 

— 

68 

-  96 

Do. 

m. 

-156 

— 

80 

-122 

Do. 

m. 

-146 

— 

66 

-  90 

Clear;  air  released;  reset  same. 

m. 

-141 

— 

66 

-102 

Cloudy. 

m. 

-154 

— 

65 

-102 

Drizzle. 

m. 

-158 

— 

66 

-124 

Clear. 

rn. 

-150 

— 

80 

-121 

Do. 

m. 

-151 

— 

66 

-  90 

Do. 

m. 

-151 

— 

64 

-  89 

Do. 

m. 

-156 

— 

67 

-108 

Do. 

m. 

-160 

— 

75 

-114 

Do. 

m. 

-159 

— 

74 

-113 

Do. 

m. 

-150 

— 

60 

-  78 

Do. 

m. 

-149 

— 

60 

-  78 

Do. 

m. 

-153 

— 

57 

-  90 

Do. 

m. 

-160 

— 

74 

-139 

Overcast. 

-152 

— 

62 

-  81 

Slightly  overcast. 

m. 

-150 

— 

55 

-  80 

Overcast. 

m. 

-158 

— 

75 

-120 

Do. 

m. 

-157 

— 

60 

-102 

Do. 

m. 

-157 

— 

60 

-107 

Do. 

m. 

-157 

— 

56 

-  96 

Clear. 

m. 

-168 

— 

78 

-132 

Do. 

m. 

-154 

— 

66 

-101 

Hazy. 

-166 

— 

74 

-102 

Do. 

m. 

-174 

— 

80 

-126 

Clear. 

m. 

-175 

— 

89 

-126 

Do. 

Some  positive  or  exudation  pressure  was  exhibited  by  all  of  the 
bores,  presumably  due  to  exudation  of  resinous  material  from  the 
canals,  with  some  participation  by  the  contraction  of  living  cells  of 
the  rays  and  xylem.  The  pressure  thus  set  up  in  the  tangential  bore 
compressed  an  air-column  from  115  to  108  mm.,  indicative  of  a  pres¬ 
sure  of  1.16  atmospheres.  A  pressure  of  1.6  atmospheres  was  found 
in  the  deep  radial  bore,  wdiile  the  shallow  radial  bore  showed  so  little 
action  in  the  initial  tests  as  to  suggest  that  the  fittings  were  defective. 


56 


HYDROSTATIC  SYSTEM  OF  TREES. 


The  water  in  the  three  bores  doubtless  injected  the  wood-cells  for  some 
distance  in  a  longitudinal  direction  and  connected  to  some  extent  with 
the  water-column  in  the  outer  layers.  The  irregular  increase  of 
suction  in  consequence  of  this  capillary  movement  of  water  aw^ay  from 
the  bore  extended  over  such  long  periods  that  the  daily  variation  was 
difficult  to  determine.  Some  slight  movement  may  take  place  through 
the  walls  but  capillary  action  would  be  through  the  minute  perfora¬ 
tions  of  the  membranes  of  the  pits,  and  would  be  much  slower  than  in 
the  vessels  and  large  conduits  of  the  walnut  and  oak. 

A  week  after  the  bores  had  been  made  it  was  seen  that  variations 
in  suction  in  the  tangential  and  deep  radial  bores  showed  an  increase 
throughout  the  day,  while  a  diminution  took  place  in  the  shallow 
bore.  Then  on  September  8,  suction  w~as  high  morning  and  evening 
with  a  minimum  at  mid-day,  while  a  progressive  decrease  took  place 
throughout  the  day  in  the  shallow  radial  bore.  Finally  on  September 
21,  after  various  adjustments  that  made  comparisons  of  some  value, 
all  showed  high  suction  in  the  morning,  a  minimum  at  mid-day,  and 
an  increase  by  4  p.  m.  Trunk  temperatures  of  a  walnut  tree  near  by 
were  13°,  25°  and  20°  C.  A  similar  variation  was  seen  on  the  following 
day.  A  lessened  suction  in  the  mid-day  period  of  high  temperature 
could  not  be  attributed  to  increased  tension  in  the  water-column, 
which  would  have  the  reverse  effect,  but  must  have  been  due  to  expan¬ 
sion  of  the  gases  in  the  old  wood  as  is  discussed  at  length  in  con¬ 
nection  with  the  observations  on  the  walnut.  Movements  of  both 
air  and  water  encounter  much  greater  resistance  in  the  stem  of  the 
pine  than  in  the  dicotyledonous  trees,  and  the  variations  are  not  so 
clear-cut  or  so  readily  correlated  with  external  conditions. 

The  records  show  that  on  many  days  suction  lessened  continuously 
throughout  the  day.  The  fact,  however,  that  it  was  greatest  at  dawn 
at  the  time  of  lowest  temperature  indicates  the  dominance  of  changes 
in  volume  in  determining  the  variations. 

The  measurements  of  variations  in  suction  of  the  stump  of  the 
branch  (fig.  12  C)  show  much  more  pronounced  variations.  The 
section  to  which  the  manometer  was  clamped  was  28  cm.  in  length  and 
about  27  mm.  in  diameter,  and  it  may  be  taken  to  communicate  with 
at  least  10  layers  of  the  older  wood.  Much  water  was  drawn  into 
the  disintegrating  medulla  and  wood  and  consequently  a  large  amount 
of  air  came  out.  The  surface  exposed  by  the  cut  was  relatively  so 
small  that  not  enough  material  was  exuded  to  set  up  a  positive  pressure. 

Daily  records  were  made  by  September  1,  of  —13,  —5  and  —80; 
September  8,  130,  84  and  130;  September  14,  130,  81  and  108;  Sep¬ 
tember  21,  78,  20  and  66.  These  were  ample  evidence  of  the  effect  of 
the  expansion  and  contraction  of  gases  in  the  system,  as  may  be  seen 
by  reference  to  trunk  temperatures  of  Juglans.  Weather  conditions, 


TESTS  OF  STUMP  AND  BORES  OF  PINE  TREES. 


57 


Fig.  12. — Monterey  pine  No.  XV  with  manometers  attached  to  a  deep  radial  bore  (A),  a  tan- 
tential  bore  (B),  a  shallow  radial  bore  (D),  and  to  a  stub  of  a  branch  (C).  A  diagram  of  the 
bores  is  given  in  lower  right-hand  corner. 


58 


HYDROSTATIC  SYSTEM  OF  TREES. 


other  than  those  of  clear  days  and  nights,  induce  variations  not  so 
easily  analyzed. 

Maximum  suction  of  —116  to  —158  mm.  Hg.  was  observed  in  the 
tangential  bore;  —43  to  —146  in  the  deep  radial  bore;  —115  to  —132 
in  the  shallow  radial  bore;  and  —100  to  —143  mm.  in  the  stump  of 
the  branch.  The  greatest  daily  variation  characterized  the  stump  of 
the  branch  which  communicated  most  freely  with  the  gases  of  the 
interior,  the  suction  sometimes  being  as  much  as  59  mm.  Hg.  less  at 
mid-day  than  in  the  morning,  while  variation  in  suction  from  the 
bases  would  be  not  more  than  a  third  this  range. 

EFFECTS  OF  ARTIFICIAL  SUCTION  APPLIED  TO  ROOTS 

AND  STEMS. 

The  conception  of  the  hydrostatic  system  of  the  pine  as  described 
in  the  opening  section  of  this  paper  is  one  which  includes  the  presence 
of  a  central  body  of  gases  enclosed  in  wood,  communicating  by  very 
minute  openings  from  tracheid  to  tracheid  and  by  the  trachese  when 
present.  Exchange  with  the  atmosphere  is  reduced  to  a  minimum, 
and  actually  takes  place  only  across  the  membranes  of  the  absorbing 
parts  of  the  roots  and  through  the  walls  of  transpiring  leaves. 

The  presence  of  such  a  body  of  gas  in  the  central  wood  may  be 
considered  as  offering  some  of  the  features  of  the  air-chamber  in  a 
pump.  It  is  obvious  that  when  a  stem  or  branch  is  cut  across  and 
its  entire  cross-section  connected  with  a  pump  or  gage,  that  the  unusual 
mechanical  conditions  created  can  not  be  easily  analyzed. 

Furthermore,  when  comparisons  are  made  between  the  effects 
of  suction  applied  at  one  end  and  pressure  applied  at  the  other,  it  will 
be  found,  for  example,  that  the  effects  of  an  exhaust  of  0.5  atmosphere 
are  not  identical  with  those  resulting  from  the  application  of  equivalent 
pressure  at  the  other.  No  detailed  examination  of  this  matter  is  to 
be  reported  here,  but  mention  was  made  of  such  differing  results  in 
a  previous  publication,  which  concerned  the  path  of  introduced  solu¬ 
tions  chiefly.1  It  seems  clear  that  most  of  the  current  generalizations 
on  resistance  of  sap  flow  through  stems  and  transpiration  pull  must 
be  revised  in  accordance  with  the  conception  of  the  hydrostatic 
system  as  presented  in  this  paper.  This  is  well  illustrated  by  the 
following  experiments  in  absorption  and  conduction  of  sap  by  preva¬ 
lent  methods,  which  were  carried  out  in  1925. 

June  1^.  A  branch  a  meter  long  with  leader,  terminal  whorl  of  3  and  a 
lower  whorl  of  4  branches,  cut  from  crown  of  pine  was  set  in  upright  position 
and  a  manometer  filled  with  water  was  clamped  to  base.  The  entrance  of 
water  into  the  stem  was  accompanied  by  extension  of  air  into  leading  tubes, 

1  MacDougal,  D.  T.  Comparative  conduction  under  suction  or  transpirational  pull,  and  under 
pressure  basally  applied.  Pp.  21-27  in  “Reversible  variations  in  volume,  pressure,  and  move¬ 
ments  of  sap  in  trees,”  Publ.  365,  Carnegie  Inst.  Wash.,  1925. 


ARTIFICIAL  SUCTION  APPLIED  TO  ROOTS  AND  STEMS. 


59 


and  the  amount  of  air  coming  out  was  increased  when  mercury  was  introduced 
into  the  U  tube  (instrument  as  in  fig.  3).  Air  was  continually  pulled  out  of 
the  stem  at  such  a  rate  that  suction  no  higher  than  10  mm.  Hg.  was  registered. 

During  the  ensuing  48  hours,  water  was  taken  up  at  a  rate  of  25  to  40  ml. 
in  24  hours.  The  preparation  stood  in  a  skylighted  and  warmed  room. 

June  16.  At  8h30m  a.  m.  the  manometer  was  replaced  by  a  vertical  tube 
filled  with  water  and  standing  in  a  dish  of  mercury.  Absorption  by  the  stem 
through  its  base  raised  a  column  of  Hg.  80  meters  in  the  first  15  minutes,  and 
no  air  was  drawn  out  of  the  stem.  The  mercury  rose  in  a  tube  2  mm.  in 
diameter,  and  hence  the  amount  of  water  absorbed  was  about  0.5  ml. 

At  9  a.  m.  the  column  had  risen  to  90  mm.,  or  an  additional  10  mm.  in 
15  minutes.  At  9h15m  the  column  had  fallen  to  15  mm.,  and  drawn  some  air 
from  the  stem.  When  this  air  was  released  and  the  water-column  again 
brought  to  the  base  of  the  stem  in  repeated  tests,  air  would  be  drawn  from  the 
stem  at  lesser  suction  values.  Such  free  communication  was  probably 
through  the  cortex  to  the  outside  air,  while  at  the  same  time  the  gases  in  the 
medulla  and  protoxylem  would  expand  under  suction  and  some  would  escape 
into  the  tube. 

A  small  pine  tree,  3  meters  in  height,  was  cut,  the  leader  was  removed, 
and  the  end  connected  by  a  clamped  rubber  hose  with  a  pump,  while  the  base 
was  set  in  a  vessel  containing  fuchsin  1-1000  in  water.  During  the  next  two 
days  the  pressure  was  repeatedly  raised  by  suction  to  750  mm.  Hg.  When 
the  pump  was  cut  off,  the  column  would  fall  about  40  mm.  in  15  minutes,  and 
the  resistance  did  not  change  much  in  the  2  days  the  experiment  was  con¬ 
tinued.  The  tree  was  dissected  50  hours  after  the  experiment  had  been  begun. 
The  dye  had  ascended  to  the  uppermost  of  the  four  whorls  of  branches,  a 
distance  of  1.5  meters,  which  would  imply  an  average  rate  of  3  cm.  per  hour. 
In  this,  as  in  previous  experiments  in  which  the  pump  was  connected  with  the 
entire  stem,  the  rate  of  such  conduction  of  dye  did  not  seem  to  be  greatly 
affected,  although  some  accelerations  have  been  found.  It  is  plainly  evident 
that  the  application  of  suction  to  the  entire  end  of  the  stem  would  produce 
results  not  directly  comparable  to  the  action  of  transpiring  surfaces  in  leaves 
connected  directly  and  only  with  the  continuous  water-column  in  the  sep¬ 
arate  layers  of  newer  wood,  in  which  radial  communication  is  very  restricted. 
This  would  also  apply  to  roots,  as  shown  by  the  following  experiment. 

July  7.  Section  of  root  of  Monterey  pine,  a  meter  in  length,  15  mm.  in 
diameter  at  the  larger  end  and  10  mm.  at  the  smaller,  was  connected  at  the 
larger  end  with  the  air  pump,  and  the  smaller  was  stepped  in  a  vessel  contain¬ 
ing  a  fuchsin  solution.  After  operation  of  the  pump  maintaining  a  column 
of  Hg.  740  to  750  mm.  for  about  8  hours  with  intervals,  the  dye  had  been 
pulled  to  a  length  of  only  about  85  cm.  The  color  was  not  seen  in  the  central 
part,  but  stained  the  other  4  layers  with  fair  uniformity  to  a  point  a  few 
centimeters  from  the  basal  end,  where  it  was  seen  in  2  segments  only,  and 
came  farthest  in  the  outermost  layer. 

A  basal  section  about  12  cm.  long  was  left  connected  with  the  pump,  and 
when  the  free  end  was  dipped  in  color,  liquid  and  color  came  through  inside 
of  a  few  minutes.  No  liquid  came  through  the  whole  length.  This  is  in 
accord  with  previous  results  in  which  no  liquid  was  extracted  by  suction  on 
the  whole  cross-section  on  any  stem  or  root  of  the  pine  of  a  length  of  more 
than  a  few  centimeters.  On  the  other  hand,  liquid  may  be  pulled  through 
a  root  of  the  oak  very  quickly.  A  section  a  meter  in  length,  18  mm.  in 
diameter  at  the  large  end,  was  connected  with  the  pump,  and  the  smaller 
end,  16  mm.  in  diameter,  was  dipped  in  a  fuchsin  solution.  The  pump  was 
started,  and  as  the  column  of  mercury  rose  quickly  in  the  barometric  gage, 


60 


HYDROSTATIC  SYSTEM  OF  TREES. 


color  was  drawn  in  quantity  through  the  root.  This  occurred  within  a  few 
seconds  and  before  the  suction  had  reached  that  necessary  to  sustain  a  column 
of  700  mm.  Hg.  The  dye  was  found  in  all  layers,  but  most  abundantly  in 
the  second  from  the  outside. 

APPLICATION  OF  SUCTION  TO  ENDS  OF  LAYERS  OF  WOOD 

CARRYING  WATER-COLUMN. 

In  view  of  the  above  facts,  experiments  were  planned  by  which 
suction  might  be  applied  only  to  layers  carrying  the  column  of  ascend¬ 
ing  water,  with  the  avoidance  of  complications  arising  from  the  action 
of  the  body  of  gases  in  older  wood  or  vessels. 

June  18.  A  small  redwood  tree,  15  cm.  in  diameter  at  the  base,  was  cut 
near  Rocky  Creek,  16  miles  from  the  Laboratory,  the  stem  was  cut  higher 
up  and  the  2-meter  length  thus  secured  was  securely  and  quickly  sealed  at 
both  ends  with  a  heavy  oil  which  was  also  applied  to  the  stumps  of  branches. 
The  preparation  was  brought  to  the  Laboratory.  A  few  hours  later,  the  base 
was  neatly  trimmed  with  an  axe  and  stepped  into  a  vessel  containing  water. 
On  the  following  day  a  hole  8  mm.  in  diameter  and  8  cm.  in  depth  was  bored 
in  the  apical  end  in  such  manner  as  to  tap  the  seventh,  eighth,  and  ninth 
layers.  A  short  section  of  tube  was  screwed  securely  in  place  and  connected 
by  pressure  hose  with  an  air  pump  (fig.  14).  The  stem  was  excentric,  and 
the  layers  were  thin,  the  outermost  four  being  not  much  more  than  1  mm. 
in  thickness.  The  base  was  stepped  into  a  vessel  of  acid  fuchsin  at  2h16m 
p.  m.,  and  the  pump  quickly  raised  a  pressure  that  sustained  a  barometric 
column  of  740  mm.  Hg.,  and  liquid  was  drawn  from  the  bore  almost  imme¬ 
diately.  The  final  length  of  the  stem  was  1.8  meters  and  a  core  the  size  of 
the  bore-hole  from  end  to  end  would  have  had  a  volume  of  90  ml.  During 
the  course  of  the  first  two  hours,  240  ml.  of  liquid  were  drawn  out  of  the  stem 
and  the  flask  was  so  nearly  filled  that  the  pump  was  stopped.  The  baro¬ 
metric  column  dropped  rapidly.  The  preparation  was  allowed  to  stand  over 
night.  The  pump  was  started  at  7h55m  a.  m.  and  water  appeared  in  the  tube 
screwed  into  the  bore  within  90  seconds.  At  the  end  of  an  hour  in  which 
the  pressure  held  up  a  column  of  Hg.  740  mm.  in  height,  90  ml.  of  sap  had 
been  extracted;  240  ml.  had  accumulated  in  the  flask  up  to  the  beginning  of 
this  period. 

The  pump  was  operated  from  9  a.  m.  to  12  noon  during  which  time  190  ml. 
additional  sap  was  collected,  a  total  of  420  ml.  in  6  hours’  operation.  It  is 
estimated  that  the  dye  came  through  after  5  hours,  when  about  400  ml.  of 
sap  had  been  drawn  out.  The  bore  extended  the  length  of  the  section  and 
would  have  a  volume  of  90  ml.  This  would  imply  that  the  sap  of  a  tract 
five  times  the  volume  of  the  core  had  been  extracted  and  that  the  longitudinal 
movement  was  at  an  average  rate  of  36  cm.  per  hour. 

The  preparation  was  allowed  to  rest  an  hour,  then  the  pump  was  operated 
for  an  hour,  during  which  time  100  ml.  of  sap  was  extracted,  152  ml.  in  all. 
It  is  to  be  seen  that  the  amount  so  drawn  out  is  greater  in  an  hour  than  an 
average  of  a  2  or  3  hour  run  of  the  pump.  The  slower  rate  may  be  attributed 
to  the  depleted  condition  of  the  conduits  after  an  extended  run  of  the  pump. 
The  barometer  column  attached  to  the  system  was  maintained  singularly 
near  740  mm.  during  the  6  hours  of  the  experiment,  and  no  change  in  resis¬ 
tance  could  be  detected.  The  pump  was  now  connected  with  a  similar 
bore-hole  in  a  radius  about  100°  from  the  first  and  opening  chiefly  in  the 
fourth,  fifth  and  sixth  layers.  Liquid  was  seen  in  the  tube  within  a  few 


SUCTION  APPLIED  TO  LAYERS  OF  WOOD  CARRYING  WATER  COLUMN.  61 


seconds  after  the  pressure  of  suction  ran  up  to  740  mm.  Hg.,  and  the  rate  of 
extraction  was  obviously  more  rapid.  The  pump  was  stopped  at  the  end  of 
an  hour  and  180  ml.  of  liquid  was  measured  in  the  receiver.  The  high  rate 
of  extraction  is  attributed  to  connection  with  more  recently  formed  wood  in 
the  second  bore  than  in  the  first.  No  color  was  seen  in  the  last  extract. 

The  pump  was  operated  on  the  following  day  after  a  rest  of  16  hours. 
270  ml.  of  sap  were  extracted  in  the  first  100  minutes,  which  was  at  the  rate 
not  widely  different  from  that  shown  by  the  same  bore  on  the  previous  day. 
Dye  appeared  in  the  extracted  sap  when  this  amount  had  been  drawn  out 
from  the  bore.  It  was  noted  that  the  resistance  remained  about  the  same, 
the  manometer  column  standing  near  740  mm.  Hg.  throughout. 

The  pump  was  now  operated  another  hour,  when  a  tinge  of  color  was  seen 
in  the  extract.  Its  apparent  rate  of  transmission  had  been  at  the  rate  of 


Fig.  13. — Range  of  air-temperature  and  of  suction  in  Monterey  pine  No.  6.  A,  suction  in  tan¬ 
gential  bore  with  only  slight  progressive  increase,  and  only  slightly  lessened  during  period 
of  high  air-temperature.  B,  suction  by  stub  of  branch,  increasing  progressively  and  lessened 
during  period  of  high  air-temperature. 


45  cm.  per  hour,  though  this  may  be  subject  to  some  correction  by  the  dif¬ 
fusion  of  dye  upward  in  the  stem.  180  ml.  of  sap  had  been  extracted,  showing 
a  fairly  uniform  rate.  The  earlier  part  of  the  extract,  the  first  200  c.c.,  had 
an  opaline  tinge. 

A  new  bore  3  mm.  in  diameter  and  3  cm.  deep  was  now  made  in  the  third 
and  fourth  layers,  equidistant  from  the  two  previous  bores.  The  pump  was 
operated  for  an  hour  and  12  ml.  of  sap  was  extracted.  The  preparation  was 
allowed  to  rest  20  hours,  when  the  pump  was  operated  for  2  hours,  during 
which  the  resistance  as  indicated  by  the  barometric  column  sustained  was 
750  mm.  Hg.,  which  was  slightly  greater  than  in  previous  operations.  About 
25  ml.  of  sap  were  extracted  in  this  2-hour  run.  Dye  was  pulled  farthest  in 
young  small  stems  rather  than  in  old  ones  (Publ.  350,  p.  31  and  p.  82) 
and  conduction  was  greatest  in  the  second  layer  in  some  cases,  and  in  the 
fourth  in  others  (2  yrs.  old?).  (See  also  Publ.  365,  p.  20.)  The  pump  was 


62 


HYDROSTATIC  SYSTEM  OF  TREES 


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SUCTION  APPLIED  TO  LAYERS  OF  WOOD  CARRYING  WATER  COLUMN.  63 


started  again  after  only  a  few  minutes’  intermission,  the  resistance  rising 
quickly  to  about  750  mm.  Hg.  Dye  was  seen  in  the  extract  after  about  4- 
hours’  operation  of  the  pump.  Calculated  on  the  basis  of  the  entire  length, 
the  color  had  moved  at  the  rate  of  45  cm.  per  hour.  The  pressure  of  the 
dye  in  the  lower  part  of  the  section  would  make  a  slightly  amended  esti¬ 
mate.  The  pump  was  now  stopped.  The  barometric  column  fell  slowly  and 
after  3  hours  a  total  of  65  ml.  of  sap  had  been  extracted.  This  amount  was 
drawn  out  in  one  hour  of  full  pressure  (750  mm.  Hg.)  and  3  hours’  lessening 
pressure,  which  w'as  down  to  250  mm.  at  the  end. 

Dissection  of  the  stem  at  this  time  showed  that  the  dye  had  ascended 
in  all  layers  about  60  cm.,  or  one-third  the  length  of  the  section.  Above 
this  the  three  conducting  tracts  leading  to  the  bore-holes  were  plainly  marked. 
Midway  of  the  stem,  the  first  twro  and  larger  streams  had  enlarged  by  dif¬ 
fusion  to  give  color  to  a  strip  3  or  4  cm.  tangentially  and  in  6  to  8  layers. 
The  strictest  channel  was,  of  course,  the  most  recent,  leading  to  the  smallest 
bore;  20  cm.  from  the  terminus  it  was  but  1  cm.  in  width  tangentially,  and 
occupied  but  one  layer  of  wood,  that  of  the  previous  year.  The  dye  leading 
to  the  larger  bores  made  in  inner  layers  had  not  diffused  sufficiently  to  be 
visible  on  the  freshly  bored  surface  for  30  cm.  below  the  end. 

The  layers  stained  seemed  to  be  determined  in  part  by  those  tapped,  and 
modified  by  tangential  and  radial  diffusion.  Movement  in  a  radial  direction 
is  least.  Not  more  than  one  or  two  layers  inwardly  or  outwardly  from  the 
conduits  connected  with  the  bore  receive  the  dye.  An  acidity  test  of  the 
extracted  sap  from  the  second  bore  showed  it  to  be  pH  6.4,  or  very  nearly 
neutral. 

The  first  use  of  the  above  method  of  application  of  suction  directly  to  the 
layers  carrying  the  water-column  was  made  on  June  12,  1925,  when  the  basal 
end  of  a  section  of  a  trunk  of  a  Monterey  pine  180  cm.  long,  10  cm.  diameter 
at  the  base,  7  cm.  at  the  upper  end,  cut  on  the  previous  day,  was  stepped  into 
a  dish  of  water,  and  the  upper  end  as  well  as  surfaces  of  stumps  of  branches 
coated  with  a  stiff  lubricating  grease.  This  was  done  to  prevent  water- 
loss  and,  also,  to  provide  for  the  least  conduction.  On  the  following  morning 
a  hole  8  mm.  in  diameter  and  25  deep  was  bored  longitudinally  in  the  wood  of 
1923  and  1924.  A  short  section  of  metal  tube  was  screwed  into  this  hole  and 
connected  with  the  air  pump.  The  surface  around  the  tube  was  sealed 
securely.  A  short  section  of  the  base  was  cut  off  cleanly  with  the  saw,  and 
this  was  stepped  into  a  vessel  containing  acid  fuchsin  1-1000  in  water.  When 
the  pump  was  started  the  system  was  exhausted  to  sustain  740  mm.  Hg. 
■within  a  few  seconds.  The  first  drops  of  liquid  drawn  into  the  receiver  were 
tinged  with  the  dye.  This  occurred  within  5  minutes,  so  much  sooner  than 
expected  that  the  time  was  not  noted  more  exactly.  Liquid  had,  therefore, 
been  drawn  up  through  the  stem  by  an  unbalanced  pressure  of  0.97  atmos¬ 
phere;  in  connection  with  a  lessened  vapor  pressure  at  the  upper  end  this 
rate  would  be  36  cm.  per  minute. 

Sap  was  drawn  out  as  the  pressure  in  the  sj'stem,  after  being  cut  off  from 
the  pump,  fell  to  720  mm.  Hg. 

After  the  method  had  been  used  with  such  signal  success  with  the  redwood, 
a  long  series  of  tests  were  made  with  the  Monterey  pine  to  test  the  rate  and 
path  of  conduction,  to  obtain  sap  from  the  separate  layers,  and  to  measure 
further  the  effects  of  suction  directly  to  the  sap-carrying  layers. 

June  2I+.  A  small  pine  10  meters  in  height  was  cut  off  near  the  base,  the 
surfaces  smeared  with  heavy  grease,  and  a  section  2.35  cm.  long  brought  into 
the  Laboratory.  The  base  showed  12  annular  layers,  and  the  apical  end, 
which  was  10  cm.  in  diameter,  8  layers.  A  bore  6  mm.  in  diameter  was  made 


64 


HYDROSTATIC  SYSTEM  OF  TREES. 


into  the  second  and  third  layers  from  the  upper  end.  These  layers  had  a 
thickness  of  5  and  11  mm.  respectively.  A  brass  tube  was  screwed  into  this 
hole  and  connected  with  the  air  pump.  A  short  section  was  sawed  from  the 
base,  which  was  stepped  into  a  vessel  of  fuchsin  at  once. 

The  pump  was  started  at  8h28m  a.  m.  and  the  pressure  was  raised  to  740 
mm.  Hg.  wdthin  10  seconds.  Within  30  seconds  liquid  appeared  in  the  tube 
inserted  in  the  bore.  At  the  end  of  an  hour  120  ml.  of  liquid  had  been  drawn 
out.  The  pump  was  started  again  at  9h40ra  a.  m.  At  llh15m  a.  m.,  265  ml. 
of  sap  had  been  extracted,  at  a  rate  of  about  165  ml.  per  hour,  which  was 
slightly  greater  than  during  the  first  hour.  The  connection  was  refitted,  and 
the  pump  started  again  at  llh20m.  Some  color  was  visible  in  the  first  sap 
that  came,  which  ran  into  the  flask  undiluted.  It  could,  therefore,  be  said 
that  the  color  came  through  in  2.75  hours.  The  length  of  the  stem  was 
2.35  meters.  The  rate,  therefore,  was  over  95  cm.  per  hour. 

Two  days  later  the  dissection  of  the  stem  showed  that  the  dye  had  been 
drawn  up  in  amount  sufficient  to  leave  a  stain  in  a  wide  sector  drawn  by 
suction  in  the  larger  bore,  which  tapped  the  second  and  third  layers.  The 
effects  of  suction  on  the  outer  layer  were  not  determinate.  The  heavy  nodes 
and  twisted  wood  made  it  impossible  to  connect  another  streak  of  color  with 
the  smaller  bore,  though  it  was  probably  caused  by  the  action  of  the  pump. 

A  small  tube  (fig.  8A),  external  diameter  3  mm.,  was  inserted  in  bore  in 
external  layer  formed  in  the  current  year.  The  pump  was  started  at  llh45m 
a.  m.  At  2  p.  m.  112  ml.  of  sap  had  been  extracted,  which  was  at  the  rate  of 
50  ml.  per  hour.  An  analysis  of  this  extract  from  the  outermost  layer  showed 
a  content  of  reducing  sugars  of  0.27  gram  per  1,000  ml.  sap  and  an  acidity 
of  pH  5.6. 

The  sap  of  the  first  sample  taken  from  the  second  and  third  layers  3  hours 
previously  had  a  sugar-content  of  0.1644  gram  per  1,000  ml.  sap  and  pH  5.4. 
A  second  sample,  obviously  diluted,  had  a  sap  pH  5.5  and  a  sugar-content 
of  0.1336  gram  per  1,000  ml.  of  sap. 

The  pump  was  operated  on  the  small  bore  in  the  outermost  layer  from 
1 1  h45m  a.  m.  until  2  p.  m.,  then  from  2  to  3h45m  p.  m.,  at  which  time  color 
was  seen.  The  pump  was  stopped  after  4  hours’  total  operation,  leaving  the 
bore-hole  connected  with  the  chambers  evacuated  by  the  air  pump  and  stand¬ 
ing  at  740  mm.  Hg.  This  was  seen  to  fall  but  slowly  by  withdrawal  of 
material  from  the  stem. 

On  the  following  morning,  the  column  of  Hg.  exerting  a  suction  on  the  stem 
had  fallen  to  0.  The  operation  of  the  pump  for  1.75  hours  and  the  subse¬ 
quent  lessening  pull  of  the  barometric  column  had  extracted  75  ml.  of  sap. 
No  color  was  apparent  after  a  total  maximum  suction  of  5  hours  in  addition 
to  this  decreasing  pull. 

The  amount  of  liquid  collected  was  equivalent  to  that  which  would  be 
extracted  in  3.5  hours’  operation  of  the  pump.  It  may  be  said,  therefore, 
that  extraction  of  sap  from  this  outermost  layer  for  nearly  6  hours  failed 
to  draw  color  through  the  stem.  This  was  in  the  basal  part  in  which  fuchsin 
does  not  often  diffuse  upwardly  at  any  rate  comparable  to  that  by  which  it 
ascends  in  older  layers. 

The  section  of  the  trunk  2  meters  in  length  was  now  taken  for  examination. 
The  basal  end  had  stood  in  a  vessel  of  water  for  48  hours.  The  heavy 
branches  had  been  trimmed  from  the  four  nodes  included.  The  stumps  and 
the  upper  end  had  been  thickly  coated  with  heavy  grease  where  the  cuts  wrere 
made.  The  upper  end  was  65  mm.  across,  showing  6  layers  of  wood,  of  which 
the  outermost  was  54  mm.  in  thickness.  The  small  tube  was  inserted  in  a 
bore  5  mm.  in  diameter  and  3  cm.  long  in  this  layer,  and  the  pump  was  started 


PRESSURES  INDUCED  BY  SUCTION  APPLIED  TO  ENDS  OF  STEMS.  65 


at  7h40ra  a.  m.  Within  a  minute  extraction  was  to  be  seen.  The  base  of  the 
section  was  in  a  vessel  of  fuchsin  1-1000  in  water. 

In  2  hours  60  ml.  of  sap  were  drawn  off  from  the  outer  layer.  The  tube  was 
reset  in  the  second  layer  and  the  pump  started  at  9h30m  a.  m.,  the  pressure 
rising  to  740  mm.  at  once  and  sap  flow  occurring  within  a  few  seconds. 
The  first  sample  from  the  outer  layer  had  a  sugar  content  of  0.2  gram  per 
1,000  ml.  with  pH  5.4. 

The  extract  during  2-hours>  operation  of  the  pump,  with  the  small  tube 
connected  with  the  second  layer,  amounted  to  72  ml.  The  tube  was  now 
connected  with  a  bore  in  the  third  layer  at  llh30m  a.  m.  At  2  p.  m.  a  total  of 
195  ml.  of  sap  had  been  extracted,  which  was  at  the  rate  78  ml.  per  hour. 
This  was  greater  than  the  rate  in  the  first  layer,  which  was  30  ml.  per  hour, 
and  the  second  layer,  36  ml.  per  hour. 

The  sap  from  the  second  layer  had  a  sugar  content  of  0.0538  gram  per 
1,000  ml.  with  pH  5.6.  The  sap  of  the  third  layer  had  a  sugar  content  of 
0.0696  gram  per  1,000  ml.  sap.  The  fitting  was  operated  on  the  fourth  layer 
from  2  p.  m.  to  4h15m  p.  m.,  obtaining  a  total  extract  of  90  ml.  of  sap  in  2.25 
hours,  which  was  extraction  at  a  rate  of  40  ml.  per  hour.  This  sap  had  a  sugar 
content  of  0.0618  gram  per  liter  and  an  acidity  denoted  by  pH  5.4.  The 
pump  was  stopped  at  4  p.  m.  and  the  bore  (in  the  fourth  layer)  was  allowed  to 
remain  in  connection  with  the  collecting  flasks,  which  had  a  total  capacity 
of  about  1.5  liter.  The  slow  equalization  of  this  pressure  took  place  during 
the  night  with  the  extraction  of  about  130  ml.  of  sap.  The  system  was  again 
exhausted  and  allowed  to  draw  on  the  stem  with  slow  equalization.  This  was 
begun  at  7h30m  a.  m.  Three  hours  later  the  mercury  had  fallen  to  150  mm., 
and  extraction  was  still  going  on  very  slowly,  during  which  time  70  ml.  of 
sap  had  been  extracted.  During  the  previous  night  total  equalization  had 
extracted  100  ml.  The  pump  was  now  operated  to  bring  the  mercury 
column  up  to  200  mm.  at  10h30m  a.  m.  when  the  connection  was  cut.  By 
inference  30  ml.  of  sap  had  been  extracted  below  this  pressure  during  the 
previous  night. 

It  is  to  be  noted  that  extraction  of  the  liquid  was  accompanied  by  a  contin¬ 
uous  appearance  of  air-bubbles.  These  were  probably  gases  released  from 
solution  under  the  lessened  pressure. 

The  pressure  ran  down  from  120  to  40  mm.  in  5  hours,  with  only  a  slight 
extraction  of  material.  Resistance  varies  enormously  with  speed.  It  is  to  be 
inferred  that  an  actual  movement  of  liquid  in  a  stem  2  meters  long  may  be 
produced  by  as  small  a  suction  as  that  of  a  column  of  Hg.  40  mm.  in  height  or 
0.05  atmosphere,  a  point  to  be  determined  later. 

On  the  following  day  a  bore  8  mm.  in  diameter  was  made,  mainly  in  the 
second  layer,  which  probably  also  connected  with  some  wood  in  the  third. 
The  pump  raised  a  column  of  only  610  to  620  mm.  Hg.  in  the  extended  sys¬ 
tem  of  flasks.  Liquid  was  drawn  out  within  20  seconds  of  the  starting  of 
the  pump.  70  ml.  had  been  collected  at  the  end  of  26  minutes  and  170  ml. 
at  the  end  of  an  hour.  No  color  wTas  seen  in  this  time.  The  stem  included 
four  nodes  with  stumps  of  heavy  branches,  and  conduction  wrould  be  variously 
complicated. 

The  dissection  of  the  stem  showed  color  in  the  inner  part  of  the  first  layer 
in  one  sector,  and  parts  of  the  second  and  third  on  separated  sectors,  none  of 
which  could  be  connected  directly  with  any  of  the  bore-holes  in  the  upper 
end,  through  the  heavy  nodal  structures. 


66 


HYDROSTATIC  SYSTEM  OF  TREES. 


MODIFICATIONS  OF  PRESSURES  INDUCED  BY  SUCTION  APPLIED 
TO  ENDS  OF  STEMS,  AND  TO  SAP-CONDUCTING  LAYERS. 

The  results  of  the  experiments  described  in  the  previous  section 
make  it  evident  that  suction  on  the  terminal  end  of  any  conducting 
tract  is  communicated  longitudinally  through  the  trunk  of  the  pine 
with  but  little  effect  on  neighboring  wood.  The  effect  seems  to  be 
more  diffused  in  Sequoia .  The  slight  suction  force  necessary  to  draw 
liquid  through  a  section  of  the  stem  was  demonstrated.  Dyes  were 
conducted  at  much  higher  rates  than  in  any  experiment  in  which  the 
exhaust  was  applied  to  the  entire  E 

cross-section.  When  this  is  done 
with  a  short  section  of  a  stem,  the 
central  air-body  may  be  drawn  out 
more  or  less  completely  and  the  stem 
infiltrated  to  such  an  extent  that 
transmission  or  conduction  may  then 
go  on  as  rapidly  as  in  the  method 
by  which  suction  is  applied  to  con¬ 
ducting  layers  only.  Such  action 
may  be  connected  with  the  results 
of  experiments  previously  described, 


Fig.  15. — Diagram  showing  relative  positions  of 
bores  used  for  extracting  sap  and  measuring 
suction  in  separate  layers  of  small  pine 
trunk.  (See  Fig.  16.) 

Fig.  16. — Scheme  of  trunk,  a  diagram  of  end  of 
which  is  shown  in  Fig.  15.  The  strict  con¬ 
duction  of  sap  to  bores  F  and  C  is  denoted 
by  heavier  shading. 


PRESSURES  INDUCED  BY  SUCTION  APPLIED  TO  ENDS  OF  STEMS.  67 

in  which  suction  applied  to  the  entire  end  of  a  short  section  of  stem 
resulted  in  no  extraction  for  an  hour  or  two,  at  the  end  of  such  period 
liquid  being  drawn  through  the  stem  in  quantity.  It  is  evident  that 
in  the  specialized  application  of  suction  to  sap-conducting  layers,  a 
method  has  been  found  by  which  a  variety  of  critical  tests  of  the  forces 
concerned  in  the  ascent  of  sap  may  be  made. 

July  20.  Small  stocky  tree  of  Pinus  radiata  was  cut  and  the  basal  sec¬ 
tion  of  trunk  2  meters  in  length  was  stepped  in  a  vessel  of  fuchsin.  The 
stumps  of  branches  and  upper  end  were  sealed  with  a  hard  grease  (figs.  16 
and  17). 

A  manometer  with  open  end  was  sealed  into  a  bore  (fig.  15  A;  cut  away 
in  fig.  16)  made  in  the  third  layer  8  mm.  in  diameter  at  8h30m  a.  m.  Readings 
were  made  as  follows: 

Table  11. 


July  20, 

8h38m 

a.  m. 

—7  mm.  Hg. 

10 

a.  m. 

- .  Some  air  released ;  set  to  0. 

10  12 

a.  m. 

—  10.  By  sudden  visible  action. 

10  18 

a.  m. 

-18. 

11  05 

a.  m. 

-15. 

2  15 

p.  m. 

-14. 

4 

p.  m. 

A  bore-hole  4  cm.  (fig.  15  and  fig.  16  C)  deep  was  made  in  the  third 
layer,  the  sides  of  which  were  20  mm.  distant  from  the  sides  of  the  bore 
to  which  the  manometer  was  attached  and  connected  with  the  pump. 

July  20, 

4  30 

p.  m. 

—  14.  55  ml.  extract  which  had  a  sugar  content  of  0.69g  per  L.,  and 

pH  of  5.7. 

July  21, 

7 

a.  m. 

-11. 

A  minute  tube  (fig.  8  D)  with  a  bore  of  1.5  mm.  was  fastened  in  a  hole  in 
the  outermost  layer  on  the  opposite  side  from  the  manometer  opening  at 
9  a.  m.  When  the  pump  was  connected  and  started  sap  was  seen  in  the  tube 
within  7  minutes.  The  flow,  howrever,  was  very  slow.  Five  hours  later 
less  than  25  ml.  of  sap  having  been  obtained,  the  tube  was  dismounted  and 
cleared,  then  re-inserted,  and  the  pump  started  again.  At  4  p.  m.  50  c.c.  of 
sap  had  been  extracted.  This  had  a  sugar  content  of  0.49  gram  per  liter,  and 
an  acidity  denoted  by  pH  5.6. 


Table  12. 


July  22, 


July  23, 


7h18m 

a. 

m. 

8 

30 

a. 

m. 

9 

a. 

m. 

9 

18 

a. 

m. 

11 

a. 

m. 

11 

10 

a. 

m. 

2 

30 

P- 

m. 

3 

30 

P- 

m. 

4 

30 

P- 

m. 

6 

30 

P- 

m. 

9 

30 

P- 

m. 

7 

a. 

m. 

Suction  —12.5. 

Do  -15. 

Do  -17.5. 

Suction.  Accumulated  sap  250  ml.  in  2  hrs.  Pressure  down  in 
changing  to  16  mm. 

Suction  —17  mm.  Taken  down  200  ml.  sap.  Pressure  in  manometer 
decreased  1  in  10  minutes. 

Started  again.  Suction  ranged  740-745  mm.  Hg.  to  —7,  a  further 
diminution  of  9  mm.  in  manometer. 

Suction  —20.  420  ml.  liquid  taken  out,  tinged  with  color.  New  bore 

and  connection,  E;  manometer  set  at  0.  New  bore  30  mm.  from  old. 

Suction— 14  mm.  Hg.  in  manometer. 

Suction  —20.  180  ml.  taken  out.  Pressure  down  1  mm.  in  5 

minutes.  Reset. 

Suction  —26. 

Do  —26.  Pump  stopped,  dye  in  extract. 

Do  —10.  240  ml.  extract  of  night  before. 


The  pump  was  set  in  a  new  bore,  E  (figs.  15  and  16),  diametrically  across 
from  the  manometer.  In  2-hours,  operation  extraction  was  at  a  low  rate, 


68 


HYDROSTATIC  SYSTEM  OF  TREES. 


which  is  to  be  coupled  with  the  fact  that  the  lowered  level  of  the  liquid  in 
the  vessel  had  bared  the  lower  end  of  the  stem.  It  was  covered  with  water 
at  9h40m  a.  m.  The  manometer  which  stood  at  —10  had  been  changed  to 
—  12  in  the  pumping.  But  little  sap  was  extracted. 

The  dissection  of  the  stem  showed  that  dye  which  started  in  the  second  and 
third  on  July  22  at  7h18m  a.  m.,  had  been  carried  up  in  the  third  and  fifth 
layers  toward  the  bore-hole,  C.  The  dye  had  appeared  in  the  extract  at 
2h30m  p.  m.  after  7-hours’  operation  of  the  pump,  which  gave  conduction 
at  a  rate  of  about  25  to  30  cm.  per  hour.  When  the  stem  was  dissected  on 
the  following  day,  color  was  visible  to  a  total  length  of  about  175  cm.  in  the 
third  and  fifth  layers,  although  colored  liquid  had  been  sucked  through  as 
noted.  Dye  had  been  pulled  through  another  bore,  B,  in  the  two  outer 
layers  in  something  less  than  5  hours,  but  in  such  quantity  that  the  wood  was 
stained  in  the  two  outermost  layers  the  entire  length  of  the  stem,  indicative 
of  a  higher  rate  of  conduction. 

The  apparatus  was  now  transferred  to  the  freshly  cut  basal  section  of  a 
tree  with  an  excentric  trunk  240  cm.  long.  The  manometer  was  attached 
to  a  bore  in  the  thin  outer  layers,  and  the  pump  to  a  bore  diametrically 
across.  The  section  was  18  cm.  in  diameter  at  base  and  15  cm.  at  the  upper 
end,  which  was  well-coated  with  grease. 

The  absorption  pressure  in  the  manometer  was  raised  to  —18  mm.  Hg. 
within  5  minutes  without  the  use  of  the  pump.  15  minutes  after  starting  it 
showed  a  suction  of  —39  mm.  Hg.  At  llh45m  a.  m.,  25  minutes  after  setting 
up,  the  pressure  had  fallen  to  — 18  mm.  Hg.,  and  at  2  p.  m.  to  — 10  mm.  Hg. 

The  pump  was  started  at  llh20m  a.  m.,  and  sap  showed  in  the  tube  within 
a  few  seconds.  Extraction  proceeded  at  a  comparatively  low  rate,  but  color 
appeared  in  the  extract  in  3  hours,  giving  a  conduction  rate  of  80  cm.  per 
hour. 

July  23.  At  3h35m  p.  m.  much  air  had  accumulated  in  the  manometer, 
and  it  was  released.  The  mercury  was  set  at  0,  and  immediate  absorption 
was  visible,  which  ran  to  —8  mm.  within  3  minutes. 

The  manometer  at  4h30m  read  — 10  mm.,  and  was  apparently  unaffected  by 
the  action  of  the  pump.  The  receiver  was  emptied  of  370  ml.  of  sap,  and  the 
pump  started  again  at  a  pressure  of  —756  Hg.  The  pump  was  stopped  at  11 
p.  m.  that  evening,  and  800  ml.  of  sap  taken  from  the  receiver  the  next  morning, 
about  1,200  ml.  in  all  from  this  bore.  This  appeared  to  be  an  acceleration  of 
the  rate  of  extraction.  It  has  been  found  previously  many  times  that  the 
rate  of  extraction  rises  after  the  base  of  such  a  cut  stem  has  stood  in  watery 
solution  for  several  hours.  Extraction  from  this  bore  was  continued. 

The  manometer  had  come  to  0  with  air  accumulated  in  the  vertical  release 
tube.  The  air  was  released  and  the  mercury  set  to  0.  Almost  immediately 
suction  pressure  showed.  The  readjustment  was  made  at  8h15m  a.  m.,  and 
a  suction  of  — 15  mm.  Hg.  showed  within  15  minutes,  which  was  taken  to  be 
unaffected  by  the  suction  of  760  mm.  in  the  pump  bore,  diametrically  across 
the  trunk.  At  10  a.  m.  a  suction  of  — 18  mm.  showed  on  the  manometer. 

At  llh30m  350  ml.  of  extract  was  removed  and  the  pump  started  again. 
The  manometer  stood  at  — 18  mm.  Some  air  was  removed,  and  the  column 
reset  to  0. 

At  2  p.  m.  290  ml.  of  sap  had  been  extracted.  Connection  was  made  with 
a  new  bore  40  mm.  distant  and  the  pump  started  at  2h30m  p.  m.  Manometer 
reset  to  0  again  after  release  of  air. 

4  p.  m.  140  ml.  of  extract  removed.  Manometer  reading  —2,  not  seem¬ 
ingly  affected  by  pump  action. 


PRESSURES  INDUCED  BY  SUCTION  APPLIED  TO  ENDS  OF  STEMS.  69 


8  p.  m.  No  pressure  in  manometer.  Pump  stopped.  360  ml.  of  extract 
were  taken  out.  Pump  run  to  set  up  pressure,  then  stopped. 

At  8  a.  m.  on  the  following  morning  no  pressure  was  denoted  by  the  man¬ 
ometer,  but  some  air  had  accumulated.  The  mercury  in  the  gage  had  fallen 
to  105  in  the  12  hours  since  a  suction  of  —750  had  been  set  up  in  the  system, 
which  had  a  capacity  of  about  1.2  liter.  This  remaining  pressure  probably 
represents  resistance  at  the  velocity  approaching  the  minimum  in  the  move¬ 
ment  of  sap.  300  ml.  of  sap  were  taken  from  the  receiver  and  the  pump  started 
again.  Suctions  as  follows  were  recorded : 

Table  13. 

July  25,  —12  at  9h30m  a.  m. 

—36  at  11  a.  m.,  with  sun  shining  on  log.  250  c.c.  extract  taken  from  receiver  at  this 
time. 

3  p.  m.  Manometer  —26.  330  ml.  of  extract  removed  from  receiver. 

July  26,  8h30m  a.  m.  Manometer  stood  at  —21.  Pump  started. 

9  30  a.  m.  290  extract  removed.  Manometer  —19. 

3  p.  m.  300  ml.  extract  taken  out.  Manometer  —17  and  no  change  resulted 

while  pump  was  being  fitted  to  new  bore-hole,  the  side  of  which  was  70 
mm.  from  the  manometer  bore.  New  large  plenum  chamber  incorporated 
in  the  vacuum  series. 

July  27,  7  30  a.  m.  Manometer  —21.  Some  200  ml.  had  been  extracted  by  the  vacuum 

over  night. 

11  a.  m.  440  ml.  removed,  and  new  hole  bored  as  dye  was  beginning  to  come  in. 

The  pump  was  stopped  before  6  p.  m.,  and  on  the  following  morning  110 
ml.  of  sap  were  taken  out  of  the  receiver.  Some  dye  showed. 

Dissection  of  this  trunk  on  August  8  showed  the  dye  unequally  distributed 
in  many  of  the  layers,  comprising  about  three-fourths  of  the  trunk,  some 
diffusion  doubtless  having  taken  place  in  the  12  days  in  the  water-filled  wood 
since  the  pump  was  dismounted.  A  second  cut,  a  third  of  the  length,  about 
1  meter  from  the  upper  end,  showed  two  stained  tracts  connected  with  the  bore¬ 
holes.  The  tract  connected  with  the  first  bore  consisted  of  material  in  the 
second  and  third  layers  about  2.5  mm.  in  width,  and  the  dye  did  not  pass  the 
last  node  and  reach  the  end,  although  over  1.8  liters  of  sap  were  extracted 
through  it.  2  liters  of  sap  were  taken  from  bore  2,  and  dye  showed,  although 
the  wood  was  stained  but  half  the  length  of  the  trunk.  But  750  ml.  extract 
were  taken  from  bore  3  when  dye  showed,  and  the  wood  was  stained  the 
entire  length  when  dissection  was  made  12  days  later.  Dye  showed  in  the 
fourth  hole  when  but  300  ml.  of  sap  had  been  extracted. 

July  28.  The  extraction  tube  was  now  fastened  in  a  bore-hole  of  the 
upper  section  of  the  same  tree,  the  lower  end  of  which  had  been  stepped  in  a 
solution  of  fuchsin  the  previous  day,  when  all  stumps  of  branches  and  the 
surface  of  the  upper  end  had  been  thickly  coated  with  heavy  grease. 

July  28,  llh00m  a.  m.  450  ml.  of  extract  were  taken  from  the  receiver  and 
at  2  p.  m.  290  more.  The  last  lot  held  some  dye  and  a  new  bore-hole  was 
made  for  extraction  while  a  manometer  was  fastened  in  the  one  just  left  vacant. 

July  28,  3h4*5m  p.  m.  180  ml.  of  sap  taken. 

July  28,  8  a.  m.  360  ml.  taken  out.  Moved  connection  to  new  hole. 
Bottom  end  of  section  dry  and  extraction  could  not  be  resumed  in  old  bore. 
No  extraction  came  in  new  bore  until  liquid  had  been  poured  into  vessel  to 
cover  lower  end  of  section.  After  230  ml.  of  sap  had  been  drawm  out,  the 
extraction  wras  terminated.  . 

About  1.4  liters  were  taken  from  the  first  bore  in  the  upper  section  of  the 
trunk.  A  third  of  the  trunk  in  several  layers  wras  heavily  stained  in  con¬ 
nection  with  this  bore.  Only  230  ml.  of  sap  were  taken  from  a  second  bore, 
and  the  wood  was  stained  only  half  the  length  of  the  trunk  in  the  third  and 


70 


HYDROSTATIC  SYSTEM  OF  TREES. 


fourth  layers.  The  dye  had  gone  nearly  to  the  end  of  the  tract  in  the  first 
bore,  staining  a  width  tangentially  of  20  mm.  in  the  third  and  fourth  layers, 
in  which  the  bore  had  been  made. 

August  5,  2  p.  m.  A  small  tree  near  entrance  wTas  cut,  the  branches  taken 
off,  the  scars  being  sealed  with  heavy  grease.  The  base,  27  mm.  in  diameter, 
was  stepped  in  fuchsin.  The  apical  end,  23  mm.  in  diameter,  was  sealed 
into  a  heavy  rubber  hose  and  the  air-pump  started  at  3  p.  m.  After  some 
difficulty  in  making  the  connection  good,  the  suction  was  raised  to  —745  mm. 
Hg.  After  several  minutes  the  stem  was  inverted,  but  no  extraction  had 
taken  place  in  repetition  of  previous  experiences. 

A  transverse  cut  was  made  in  the  stem  60  cm.  from  the  base  by  means  of 
a  saw,  which  half  severed  the  stem.  This  was  filled  with  stiff  grease  which 
was  liberally  piled  on  the  cut. 

No  extract  in  an  hour. 

Pump  overset;  connections  and  suction  restored  by  4h30m  p.  m.,  745  mm. 
Hg.,  and  pump  stopped. 

August  5,  8h30m  a.  m.  The  suction  stood  at  —400  mm.  from  the  previous 
day,  showing  good  connections  and  high  resistance.  No  extract.  Pressure 
raised  again  to  7h45m  mm. 

August  6,  2h30m  p.  m.  The  suction  set  up  30  hours  previously  had  fallen 
to  —200  mm.,  and  a  few  cubic  centimeters  extract  had  collected  in  the  tube. 
The  pump  was  now  operated  for  a  few  minutes  until  the  pressure  again  stood 
at  —745  mm.,  after  which  it  was  stopped. 

August  7,  9  a.  m.  Column  stood  at  300  mm.  with  only  a  few  drops  ex¬ 
tracted.  At  4  p.  m.,  column  down  to  —200  mm.  Pump  operated  to  bring 
pressure  up.  Several  milliliters  of  extract  seen. 

August  8,  8h8m  a.  m.  Exhaust  column  at  340  mm.  Some  extract.  Stem 
dismounted  for  dissection.  The  dye  had  come  up  in  all  of  the  8  layers  of  the 
stem  to  a  short  distance  below  the  transverse  cut,  which  was  filled  with 
grease  in  the  ordinary  manner  of  diffusion  of  such  material.  It  stopped  7 
or  8  cm.  short  of  the  cut  in  the  inner  layers,  but  showed  in  the  two  outer¬ 
most  to  within  a  few  millimeters  of  the  groove.  It  did  not  show  in  the  sector 
blocked  off  above.  The  stem  was  somewhat  irregular  and  it  was  not  easy 
to  follow  the  course  of  the  conduits,  but  it  was  apparent  that  the  dye  which 
disappeared  from  some  of  the  inner  layers  of  the  uninterrupted  half  of  the 
stem,  above  the  node  25  cm.  above  the  cut,  had  shown  some  circumferential 
diffusion  in  first  and  second  layers  in  which  it  continued,  so  that  the  un¬ 
stained  section  was  reduced  to  about  a  quarter  of  the  circumference,  a  meter 
above  the  cut.  Above  this,  by  reason  of  the  ordinary  inequalities  of  dif¬ 
fusion,  the  dye  showed  only  in  a  decreasing  section,  coming  down  to  a  narrow 
ribbon  above  a  node  25  cm.  from  the  upper  end  of  the  cut  stem,  where  the 
color  showed  only  in  the  outer  layer.  It  was  notable  that  while  the  wood 
was  stained  to  within  22  cm.  of  the  upper  end  of  the  stem,  no  color  appeared 
in  the  extract,  of  which  no  more  than  100  ml.  had  been  obtained  in  several 
hours  at  745  mm.  suction,  and  many  more  at  diminishing  pressures. 

August  11.  A  small  pine  tree  outside  of  the  main  entrance  was  cut,  the 
base  being  40  mm.  in  diameter.  The  branches  were  trimmed  and  the  scars 
sealed  with  heavy  grease.  A  section  1.8  mm.  long  was  taken  for  test  with  the 
air  pump.  The  base  was  fitted  with  a  section  of  large  rubber  tube,  tightly 
bound  round  it,  in  which  a  solution  of  fuchsin  was  placed,  this  arrangement 
allowing  the  stem  to  be  held  in  a  horizontal  position  while  suction  was  being 
applied  to  the  upper  end,  which  had  a  diameter  of  30  mm.  A  short  section 
of  heavy  rubber  hose  was  clamped  round  the  upper  end  and  connected  with 
an  air  pump  through  a  plenum  chamber  with  a  capacity  of  20  liters. 


TRANSMISSION  OF  SUCTION  APPLIED  TO  ENDS  OF  STEMS. 


71 


It  had  been  noted  in  previous  experiments  that  suction  might  be  applied 
to  the  upper  end  of  a  stem  in  this  manner  for  many  hours  without  any  ex¬ 
traction  of  sap  resulting.  This  would  come  only  after  the  stem  had  stood 
with  its  base  in  liquid  for  several  hours  with  suction  at  the  upper  end,  while 
a  tube  inserted  in  the  outer  wood  would  draw  sap  in  a  few  seconds  with  a 
vacuum  holding  up  a  mercury  column  of  745  mm.  It  has  been  held  that  the 
delay  in  extraction  when  suction  was  applied  to  the  whole  stem  was  due  to  the 
air  cushion  in  the  inner  layers  and  medulla  of  the  stem.  It  was  therefore 
arranged  to  close  off  this  air  system  and  apply  suction  to  the  ends  of  the 
conducting  wood  supposedly  filled  with  water.  To  accomplish  this  a  bore 
8  mm.  in  diameter  was  made  in  the  central  part  of  the  stem  to  a  depth  of 
about  40  mm.  This  was  filled  with  a  stiff  grease,  then  a  short  section  of 
threaded  bolt  was  screwed  into  the  bore  for  the  purpose  of  blocking  off  the 
entrance  to  the  central  air-filled  wood.  This,  of  course,  could  not  be  done 
perfectly  or  completely,  but  the  experiments  described  below  show  that 
communication  had  been  much  restricted.  A  section  of  pressure  connected 
with  the  air-pump  was  now  clamped  about  the  end  of  the  stem  thus  prepared. 
Had  the  preparation  been  perfect,  suction  could  have  been  exerted  on  the 
sap-carrying  wood  only.  The  pump  was  started  at  8h50m  a.  m.,  and  as  the 
large  plenum  chamber  was  exhausted,  extraction  began  within  10  minutes  of 
the  beginning  of  the  operation,  and  within  a  much  shorter  period  of  high 
suction.  Extraction  continued  with  a  decreasing  rate  until  llh30m  a.  m., 
when  the  exhaust  gage  stood  at  300  mm.  The  pump  was  again  operated 
to  bring  it  up  to  745  mm.  At  7  p.  m.  the  column  had  come  down  to  300  mm. 
The  pump  was  again  operated  to  exhaust  the  system. 

August  9,  8  a.  m.  On  the  following  morning  the  exhaust  column  had 
fallen  to  180  mm.,  and  a  total  of  150  ml.  of  sap  was  taken  from  the  receiver. 
This  sap  had  an  acidity  denoted  by  pH  5.6,  and  a  sugar  content  of  1.2  grams 
per  liter.  The  dissection  of  the  stem  showed  a  course  of  the  dye  much  as  in 
the  previous  stem.  The  color  came  in  all  layers  stopping  about  10  cm.  short 
of  a  saw-cut,  which  half  severed  the  stem.  Above  the  cut,  the  dye  first  came 
into  the  inner  layers  and  diffused  circumferentially,  until  at  a  distance  of 
a  meter  above  the  cut  the  dye  had  disappeared  from  the  inner  layers,  showed 
in  the  three  outer  layers  on  the  normal  flank,  and  in  the  third  and  fourth 
layers  only  of  the  flank  above  the  cut.  Above  the  last  node,  the  color  had 
gone  up  in  two  strips  in  the  outermost  layers  only  which  were  connected  with 
the  stained  wood  of  the  normal  flank  below.  The  diffusion  of  dye  had 
stained  the  wood  a  total  length  of  about  160  cm.  in  24  hours  at  a  rate  of  less 
than  7  cm.  per  hour.  It  was  not  possible  to  detect  any  color  in  the  extract. 

August  13,  8h30m  a .  m.  A  small  tree  was  cut  near  the  entrance,  the  base 
and  the  scars  of  the  branches  sealed  with  stiff  grease  and  a  section  1.9  meters 
long  cut  from  it.  The  basal  end,  30  mm.  in  diameter,  was  kept  moist  and 
was  quickly  sealed  into  a  section  of  reinforced  hose,  which  was  connected  with 
a  barometric  gage.  The  hose  and  connections  had  been  filled  with  a  fuchsin 
solution.  The  stem  being  placed  in  a  horizontal  position,  the  mercury  rose 
within  a  minute  to  20  mm.  above  the  level  in  the  cistern,  and  at  the  end  of  20 
minutes  had  attained  a  further  height  of  30  mm.  above  it.  Meanwhile,  the 
upper  end  of  the  stem  had  been  sealed  into  another  section  of  hose  connected 
with  an  air  pump  with  its  gage,  but  the  pump  was  not  operated  until  later  as 
noted  below.  Meanwhile,  the  suction  into  the  base  of  the  stem  was  denoted 
by  the  readings  shown  in  Table  14. 


72 


HYDROSTATIC  SYSTEM  OF  TREES. 


Table  14. 


Date. 

Time. 

Suction 

in 

mm.  Hg. 

Remarks. 

1925 

Aug.  13 

8h55m  a.  m. 

—  45 

9  a.  m. 

-  50 

9  05  a.  m. 

-  55 

9  10  a.  m. 

-  60 

9  15  a.  m. 

-  65 

9  20  a.  m. 

-  70 

9  25  a.  m. 

-  74 

Disturbed  and  came  down  to  —65. 

9  30  a.  m. 

-  70 

9  45  a.  m. 

-  75 

Pump  started. 

9  50  a.  m. 

-  85 

Exhaust  —700  mm.  Hg. 

9  55  a.  m. 

-100 

Do.  —745  mm.  Hg. 

10  a.  m. 

-110 

Do.  —755  mm.  Hg. 

10  05  a.  m. 

-116 

Do.  —756  mm.  Hg. 

10  10  a.  m. 

-122 

Do.  —756  mm.  Hg. 

10  30  a.  m. 

-143 

Do.  —755  mm.  Hg. 

10  45  a.  m. 

-160 

Do.  —754  mm.  Hg. 

11  a.  m. 

-180 

Do.  —753  mm.  Hg. 

11  40  a.  m. 

-200 

Do.  —745  mm.  Hg.  No  extraction  of  sap. 

1  45  p.  m. 

-290 

Pump  operated  to  bring  pressure  to  —720.  Extraction 

began  6h50m  p.  m. 

4  p.  m. 

-360 

Pump  operated  to  bring  exhaust  to  —740.  Some  ex- 

traction. 

7  p.  m. 

-425 

Exhaust  —675  mm.  Pump  operated  15  minutes. 

7  15  p.  m. 

-430 

Do.  —755  mm. 

7  30  p.  m. 

-435 

Do.  —750  mm. 

7  45  p.  m. 

-440 

Do.  —748  mm. 

Aug.  14 

5  45  a.  m. 

-455 

Do.  —475  mm.  Pump  operated. 

6  a.  m. 

-456 

Do.  —755.  Air  in  manometer;  reset  to  0  and 

pump  started. 

6  33  a.  m. 

— 

Immediate  suction  through  stem  as  column  connected 

with  plenum  chamber  rose. 

6  53  a.  m. 

-170 

Exhaust  —745  mm. 

7  a.  m. 

-240 

Do.  —730  mm. 

7  12  a.  m. 

-290 

Do.  —715  mm. 

7  35  a.  m. 

-350 

Do.  —680  mm.  Pump  operated  to  bring  exhaust 

to  —740;  extraction  proceeding. 

8  a.  m. 

Air  in  manometer  reset  at  —165  and  pump  operated 

to  bring  exhaust  up  to  —740. 

8  30  a.  m. 

-390 

Exhaust  695. 

9  30  a.  m. 

-440 

Do.  745. 

9  50  a.  m. 

-450 

Do.  725.  Pump  operated  to  —745. 

10  50  a.  m. 

-465 

Do.  670. 

11  15  a.  m. 

-470 

Do.  720. 

Aug.  15 

9  45  a.  m. 

-365 

Do.  10.  Air  released;  manometer  and  exhaust  reset 

to  0.  Pump  started  9h55m  a.  m. 

10  05  a.  m. 

-  80 

Exhaust  740.  Some  extraction. 

11  30  a.  m. 

-315 

Do.  620.  Pump  operated. 

12  15  a.  m. 

—375 

Do.  742. 

2  p.  m. 

-435 

Do.  600.  Pump  operated. 

2  25  p.  m. 

-445 

Do.  740. 

3  15  p.  m. 

-460 

Do.  675.  Pump  operated. 

4  p.  m. 

-475 

Do.  740. 

5  30  p.  m. 

-495 

Do.  740. 

Aug.  16 

7  30  a.  m. 

-405 

Do.  75.  Pump  operated  to  bring  exhaust  to  740 

and  air  released  from  other  instrument,  allowing 

column  to  fall  to  438. 

9  a.  m. 

-440 

Exhaust  740. 

9  40  a.  m. 

-470 

Do.  700.  Pump  operated. 

10  40  a.  m. 

-490 

Do.  740. 

12  15  p.  m. 

-498 

Do.  633. 

4  p.  m. 

-415 

Do.  360.  Pump  operated. 

4  15  p.  m. 

-420 

Do.  740. 

TRANSMISSION  OF  SUCTION  APPLIED  TO  ENDS  OF  STEMS. 


73 


Table  14 — Continued. 


Date. 

Time. 

Suction  in 
mm.  Hg. 

Remarks. 

1925 

Aug.  17 

7h20m  a.  m. 

-200 

Exhaust  —60.  Air  released;  manometer  set  to  0  and 

pump  started. 

7  24  a.  m. 

-  40 

Do.  -680. 

7  27  a.  m. 

-  90 

Do.  -735. 

7  30  a.  m. 

-125 

Do.  —745. 

7  45  a.  m. 

-255 

Do.  -750. 

8  a.  m. 

-330 

Do.  —725.  Pump  started  and  operated  continuously. 

8  20  a.  m. 

-380 

Do.  —745. 

8  35  a.  m. 

-425 

Do.  —745. 

9  a.  m. 

-452 

Do.  —745. 

9  30  a.  m. 

-475 

Do.  -748. 

11  a.  m. 

—  505 

Do.  —748. 

11  45  a.  m. 

-510 

Do.  -748. 

1  45  p.  m. 

-520 

Do.  —748.  Pump  stopped. 

3  30  p.  m. 

-455 

Do.  —620. 

4  50  p.  m. 

-510 

Do.  —565. 

5  15  p.  m. 

-503 

Do.  -501. 

-498 

Do.  -480. 

5  30  p.  m. 

-495 

Do.  -470. 

Aug.  18 

8  a.  m. 

-405 

Do.  -  50. 

The  temporary  rise  after  3.30  p.  m.  August  17  is  not  explainable.  The  slow 
fall  of  the  column  at  the  end  of  the  trunk  is  due  to  the  resistance  to  the  en¬ 
trance  of  air  from  the  exhaust  chamber  in  which  the  pressure  was  seen  to 
approach  atmospheric,  and  was  within  50  mm.  of  it  on  the  following  morn¬ 
ing.  Presumably  the  stem  was  more  nearly  infiltrated  with  water  than 
before.  The  pump  was  now  started  again  at  8.30  a.  m.,  and  readings  made 
as  follows : 

Aug.  18,  8h50m  a.  m.  —452  mm.  Hg.  suction  into  base  of  stem.  Exhaust  —748. 

9  30  a.  m.  —455  mm.  Hg.  suction  into  base  of  stem.  Exhaust  —748. 

The  exhaust  chamber  was  disconnected,  the  receiving  flask  turned  up  to 
immerse  the  end  and  thus  allow  water  to  be  drawn  in,  instead  of  air,  as  the 
column  at  the  basal  end  of  the  trunk  fell. 

At  10h30m  the  manometer  was  at  —405  mm.  and  no  noticeable  difference 
could  be  seen.  Exhaust  was  now  released  at  upper  end  formerly  connected 
with  the  pump,  and  this  end  was  supplied  with  water  at  atmospheric  pressure, 
the  other  end  arranged  to  show  any  suction.  This  was  manifest  at  once  and 
the  column  in  the  manometer  had  been  drawn  to  —85  mm.  at  11  a.  m.  At 
llh25m  the  column  had  risen  to  100  mm.  At  12  noon  the  column  had  fallen 
to  90  mm.;  at  2  p.  m.  it  had  come  down  to  —25  mm.,  with  marked  absorption 
of  water  at  the  upper  end. 

The  figures  given  illustrate  the  fact  that  after  treatment  for  5  days  as 
implied  in  the  preceding  tests,  water  entered  the  stem  as  by  capillarity  or 
suction  pressure.  While  water  was  being  allowed  to  enter  one  end  from  an 
open  funnel,  it  wras  being  taken  in  at  the  other  with  a  force  which  raised  the 
column  of  mercury  to  100  mm. 

The  chamber  with  a  capacity  of  20  liters  was  now  exhausted  to  sustain  a 
column  745  mm.  in  height.  When  this  had  been  done,  the  stopcock  was 
turned  to  connect  it  with  the  leading  tube  at  the  upper  end  of  the  stem. 
Suction  in  the  manometer  attached  to  the  base  rose  to  —20  mm.  within  30 
seconds.  The  pump  was  now  operated  for  40  minutes  with  the  manometer 


74 


HYDROSTATIC  SYSTEM  OF  TREES. 


at  the  base  of  the  stem  reading  —  205  mm.  At  7  a.  m.  on  the  following  day  the 
exhaust  had  fallen  to  —  355,  while  the  column  in  the  manometer  at  the  other  end 
of  the  stem,  having  been  raised  by  the  exhaust,  showed  a  lag  in  falling  so  that 
it  stood  at  —420  mm.  Operation  of  the  pump  at  llh45m  a.  m.  for  half  an  hour 
resulted  in  an  exhaust  of  740  mm.  and  a  manometer  reading  of  460  on  the 
stem.  Two  hours  later  the  exhaust  had  fallen  to  —700,  but  the  stem-mano¬ 
meter  stood  at  —470  mm. 

Table  15. 


Date. 

Time. 

Exhaust. 

Stem-manometer. 

Remarks. 

1925 

Aug.  20 

8h00m  a.  m. 

-260 

-420 

Pump  operated  for  a  few  minutes  to 

bring  exhaust  to  —740. 

9  a.  m. 

-740 

-425 

11  a.  m. 

-745 

-430 

Pump  operated  for  a  few  minutes. 

Aug.  21 

1  30  p.  m. 

-185 

-355 

Aug.  22 

1  30  p.  m. 

-350 

Pump  disconnected. 

4  p.  m. 

Reset  to  0. 

5  p.  m. 

-  60 

Aug.  23 

8  a.  m. 

-180 

11  a.  m. 

-170 

4  30  p.  m. 

-155 

Aug.  24 

7  30  a.  m. 

-215 

The  preparation  was  now  dismounted  and  the  stem  dissected.  The  dye 
had  stained  all  layers  to  the  first  node,  a  length  of  a  meter  from  the  base. 
Above  this  the  color  began  to  show  a  lessened  density  in  the  inner  layers,  and 
at  30  cm.  from  the  end  was  present  in  the  two  outer  layers  only;  extreme 
extension  of  the  dye  was  in  the  outermost  layer. 

A  repetition  of  this  experiment  seemed  desirable,  and  another  small  tree 
was  cut  and  the  upper  end  to  which  suction  was  applied  was  bored  and 
plugged  centrally  as  follows: 

August  19.  A  small  pine  near  entrance  was  cut  down,  the  branches  taken 
off,  the  scars  sealed  with  grease  as  well  as  the  base  of  the  stem,  and  taken  into 
the  laboratory.  A  short  section  of  the  base  was  sawed  off,  and  a  section  of 
pressure  hose  clamped  over  it  and  sealed.  This  was  filled  with  water  and 
connected  with  a  vertical  tube  standing  in  a  mercury  column  at  9  a.  m. 
The  base  was  27  mm.  in  diameter  and  showed  8  layers  of  wood.  The  top 
was  cut  at  a  distance  of  3.5  meters  from  the  base.  This  terminal  end  was  in 
the  internode  formed  in  1924  and  was  about  14  mm.  in  diameter.  A  hole 
8  mm.  in  diameter  was  bored  longitudinally  to  a  depth  of  3  cm.  from  the 
center  to  remove  pith  and  protoxylem,  filled  with  stiff  grease,  then  a  threaded 
metal  plug  was  screwed  in  to  complete  the  seal.  The  outer  part  of  the  wood  of 
1924  and  the  wood  of  the  present  year  were  left  exposed. 

At  10  a.  m.  the  mercury,  which  had  been  adjusted  at  the  same  level  in  the 
tube  as  in  the  cistern,  had  been  pushed  out  of  the  tube  and  some  air  had  come 
out  of  the  base  of  the  stem.  At  10h45m  a.  m.  active  absorption  had  begun 
and  a  column  70  mm.  had  been  pulled  up  in  the  manometric  column.  Other 
readings  are  given  in  Table  16. 

Extraction  of  sap  from  ends  of  branches  and  stems  of  conifers  by  suction 
is  attended  with  difficulty  when  suction  is  applied  to  the  entire  cross-section. 
Expansion  of  gases  in  the  central  gas-filled  conduits  and  wood  results  from 
the  suction  at  first.  If  the  free  end  of  the  stem  is  immersed  in  liquid  this  is 
gradually  drawn  in,  and  after  the  stem  is  approximately  infiltrated  extraction 
may  begin.  Suction  applied  in  this  manner  causes  only  slight  acceleration 
of  the  movements  of  days  in  the  ascending  sap  meshwork  or  column. 


TRANSMISSION  OF  SUCTION  APPLIED  TO  ENDS  OF  STEMS. 


r*  r 

/5 


Table  16. 


Aug.  19,  llh45m  a.  m. 

1  45  p.  m. 
4  p.  m. 

Aug.  20,  8  a.  m. 

Aug.  21,  1  p.  m. 


Stem 

Stem 

Stem 

Stem 

Stem 


—  75  mm. 
—68  mm. 
—68  mm. 
—50  mm. 
—48  mm. 


Reset  to  0;  air  released. 


0.  Air  released.  The  pump  was  now  connected  to  the 
pressure  tubing  clamped  at  upper  end  and  suction  was  applied  to  deter¬ 
mine  effect  of  such  suction  on  further  end  of  stem. 


Aug.  21, 

1  45 

p.  m. 

Pump  connected  and  operated;  exhaust  suction  at  basal  end. 

4  30 

p.  m. 

Exhaust 

—670.  Stem  —8  mm. 

4  40 

p.  m. 

Do. 

—742.  Stem  —12  mm. 

Aug.  22, 

8 

a.  m. 

Do. 

—290.  — .  Air  taken  out  of  system  at  basal  end  of  stem;  mer- 

cury  set  at  0.  Pump  started  at  8h15m  a.  m.  and  stopped  at  8h35m. 

No 

action  at  farther  end  of  stem.  Operated  at  intervals  later. 

Aug.  22, 

1 

p.  m. 

Exhaust 

-740. 

5 

p.  m. 

Do. 

—660.  Stem  —30. 

Aug.  23, 

8 

a.  m. 

Do. 

—  628.  Stem  —35. 

9  30 

a.  m. 

Do. 

—742.  Stem  —35. 

11  15 

a.  m. 

Do. 

—  640.  Stem  —28. 

4  30 

p.  m. 

Do. 

—500.  Stem  —22. 

Aug.  25, 

8  45 

a.  m. 

Pump  started  and  operated  for  15  minutes.  No  effect  at  opposite  end 

of  stem. 

11 

a.  m. 

Pump  operated  for  a  half  hour  and  stopped  with  column  at  —742. 

At 

the  end  of  an  hour  (12  noon)  the  column  at  the  farther  end  had  been 
pulled  up  to  23  mm. 

At  3h30m,  4  hours  after  the  exhaust  had  been  left  at  —742,  the  column  at  the  end  of  the 
stem  had  risen  to  90  mm.  at  which  time  the  exhaust  had  fallen  to  —630  mm 
At  4h15m  p.  m.  Exhaust  —605,  stem  —95.  Pump  operated  5  minutes  on  exhaust. 


Aug. 

26, 

7 

45 

a. 

m. 

Exhaust  chamber  stood  at  —330  and  stem  at  60  mm.  Pump  operated 

for  40  minutes. 

8 

25 

a. 

m. 

Exhaust 

-742. 

Stem 

—57  mm. 

11 

30 

a. 

m. 

Do. 

-660. 

Stem 

—45  mm.  Pump  operated  for  5  minutes  to 

bring  exhaust  to  - 

-742. 

7 

P- 

m. 

Exhaust 

-560. 

Stem 

—  60  mm.  Pump  operated  for  5  minutes. 

Aug. 

27, 

7 

40 

a. 

m. 

Pump  operated  for  5  minutes  as  stem  suction  was  at  0  and  air  was 

released  from  end. 

Aug. 

28, 

8 

30 

a. 

m. 

Exhaust 

-200. 

Stem 

—  90.  Pump  operated. 

3 

30 

P- 

m. 

Do. 

-555. 

Stem 

-85. 

Aug. 

29, 

7 

30 

a. 

m. 

Do. 

-240. 

Stem 

-6. 

Aug. 

30,  10 

a. 

m. 

Pump  started  after  connection  had  been  refitted.  Short  section  taken 

off  and  plug  again  screwed  into  the  center  of  the  stem. 

6 

P- 

m. 

Exhaust 

-500. 

Stem 

—  115.  Pump  operated  a  few  minutes. 

Aug. 

31, 

9 

a. 

m. 

Do. 

-200. 

Stem 

-8. 

Sept. 

1. 

7 

a. 

m. 

Do. 

-200. 

Stem 

-40. 

10 

30 

a. 

m. 

Do. 

-200. 

Stem 

—8.  Pump  operated. 

Sept. 

2, 

7 

30 

a. 

m. 

Do. 

-300. 

Stem 

—  180.  Pump  operated. 

11 

a. 

m. 

Do. 

-660. 

Stem 

-140. 

Suction  applied 

to  bores  made 

in  the  3  or  4  outer  layers  of  a  stem  of  the 

Monterey  pine,  the  free  end  of  which  is  immersed  in  liquid,  results  in  extrac¬ 
tion  of  sap  solutions  from  these  layers,  and  also  greatly  accelerates  the  move¬ 
ments  of  dyes  introduced  into  the  free  ends.  The  rates  of  movement  were 
seen  to  vary  in  the  pine  from  35  to  96  cm.  per  hour  under  suction  less  than  an 
atmosphere.  These  rates  suggest  the  possibility  of  much  higher  rates  of 
movement  from  tensions  of  several  atmospheres  which  might  be  set  up  in  the 
menisci  of  transpiring  cells  in  the  leaves. 

Bore-holes  or  stumps,  in  which  the  inner  gas-filled  wood  is  placed  in  condi¬ 
tion  to  absorb  water,  invariably  show  suction  which  may  not  be  due  to  less 
than  atmospheric  pressures  in  this  wood.  Capillary  action  of  conduits  and 
the  slower  passage  of  water  into  tracheids  would  set  up  “ negative  pressures/' 
sometimes  misinterpreted. 


76 


HYDROSTATIC  SYSTEM  OF  TREES. 


When  one  end  of  a  stem  is  connected  with  a  manometer,  suction  is  generally 
registered  at  once.  A  similar  fitting  at  the  other  end  of  the  stem  connected 
with  an  air  pump  gives  opportunity  to  test  longitudinal  transmission  of  suction. 

The  application  of  suction  to  bore-holes  in  selected  layers  at  measured 
distances  from  other  bores  allows  the  tangential  or  circumferential  transmis¬ 
sion  to  be  measured.  It  was  found  that  the  absorption  or  suction  was  not 
transmitted  to  half  the  circumference,  of  a  small  trunk,  and  in  fact  that  the 
maximum  action  of  a  pump  holding  up  a  column  of  Hg.  740  mm.  in  height 
did  not  show  on  a  manometer  attached  to  bores  more  than  10  mm.  distant 
tangentially. 

Transmission  of  suction  applied  to  the  entire  surface  of  the  end  of  a  small 
trunk  was  marked  in  lengths  of  3  meters,  and  presented  certain  features 
identifiable  with  the  resistance  offered  by  the  older  wood.  Thus  a  suction 
that  would  hold  up  over  740  mm.  mercury  when  transmitted  through  a 
stem  nearly  2  meters  in  length  held  up  a  column  of  520  mm.  in  a  vertical  tube 
connected  with  a  sheathing  hose  at  the  further  end,  in  one  instance,  and  sus¬ 
tained  more  than  400  mm.  in  many  other  cases.  Another  noticeable  feature 
was  the  manner  in  which,  as  the  suction  fell  at  one  end  after  stoppage  of  the 
pump,  it  would  continue  to  rise  at  the  other,  as  shown  by  the  manometer. 

SUCTION  FORCE  IN  TRUNK  OF  MONTEREY  PINE  KILLED 

BY  DEFOLIATION. 

Although  the  view  held  by  some  writers  that  the  living  cells  of 
stems  exercise  a  pumping  or  pulsatory  action  on  the  upward  movement 
has  not  found  adequate  support,  many  workers  assume  that  the  ascent 
of  sap  can  not  take  place  except  by  the  intervention  of  living  cells. 
It  has  been  proved  at  various  times  that  water  may  enter  dead  shoots 
through  a  dead  root-system,  that  the  ascending  column  may  pass 
through  sections  of  stem  that  have  been  killed,  but  the  workers  who 
accept  the  explanation  of  Dixon  as  to  the  mechanism  of  the  moving 
water-column  under  tensions  set  up  by  loss  of  water  from  the  menisci 
in  the  leaves  hold  with  him  that  the  presence  of  living  cells  is  necessary 
for  the  maintenance  of  the  sap-column.  While  the  sap-column  is 
undoubtedly  affected  by  the  action  of  the  living  cells  in  the  root,  by 
the  parenchymatous  cells  of  the  xylem  of  the  rays,  and  while  the 
suction  force  creating  the  tensions  ordinarily  originate  in  the  walls 
of  living  cells,  I  have  shown  that  elementary  colloidal  conditions  rather 
than  any  complex  of  living  material  constituted  the  sine  qua  non  of 
the  ascent  of  sap. 

This  is  based  upon  the  results  of  tests  made  with  small  trees  (6  to 
8  meters  in  height)  which  have  died  several  weeks  after  defoliation. 
The  leaves  were  removed  by  being  pulled  directly  from  their  sheaths, 
the  scar  being  quickly  sealed  by  resinous  excretions.  The  Monterey 
pine  perishes  if  older  leaves  are  removed  in  such  manner  that  only 
new  undeveloped  or  no  leaves  remain,  as  I  have  previously  described.1 
The  matter  may  be  illustrated  by  the  completed  history  of  Pine  No. 
27,  of  which  some  description  has  been  made  in  the  publication 
mentioned. 

1  MacDougal,  D.  T.  Reversible  variations  in  volume,  pressure,  and  movements  of  sap  in 
trees.  Publ.  No.  365,  1925.  (See  pp.  67-85.) 


SUCTION  IN  TRUNK  OF  MONTEREY  PINE  KILLED  BY  DEFOLIATION.  77 


This  tree  had  been  defoliated  in  January  1924,  leaving  only  the 
terminal  tufts  of  very  young  leaves.  It  had  been  noted  late  in  Novem¬ 
ber  that  nearly  all  of  these  tufts  were  brownish  and  dead.  Despite 
this  fact  some  reversible  variations  occurred,  and  a  warm  rain  on 
January  13  was  followed  by  a  notable  increase  in  diameter.  One 
tuft  wras  noted  which  retained  a  greenish  tinge.  It  is  important  to 
determine  whether  or  not  any  reversible  variation  occurred  after  all 
of  the  living  cells  had  perished. 

A  manometer  fitted  to  a  tangential  bore-hole  in  September  1924 
showed  suction  by  which  the  air-column  in  a  manometer  was  extended 
from  63  to  68  mm.,  which  was  equivalent  to  0.08  atmospheres,  or 
about  61  mm.  Hg. 

A  month  later  a  similar  fitting  showed  an  exudation  pressure  com¬ 
pressing  an  air-column  from  95  to  92  mm.  and  increase  of  0.03  at¬ 
mospheres.  A  repetition  of  the  test  showed  only  suction. 

On  January  16,  1925,  a  closer  examination  of  these  leaves  revealed 
the  fact  that  the  young  shoots  on  which  they  were  borne  were  entirely 
dead  and  all  of  the  cells  were  brown.  The  leaves  were  also  dead  and 
fell  off  as  touched.  The  dendrograph  was  continued  on  the  trunk  and 
recorded  reversible  variations  in  diameter  of  a  range  of  about  0.2  mm., 
and,  as  the  diameter  of  the  trunk  was  75  mm.,  it  is  to  be  seen  that  the 
coefficient  was  1  in  375,  which  was  not  widely  different  from  that  of 
other  small  uninjured  trees  at  the  same  time. 

Six  months  later,  when  the  brownish  granular  condition  of  the 
tips,  the  leaves,  and  all  material  external  to  the  woody  cylinder,  made 
it  obvious  that  the  tree  was  dead,  the  dendrograph  bearings  were 
cleaned,  and  arrangements  were  made  to  connect  a  manometer  with  a 
tangential  bore  50  cm.  in  depth  in  the  wood,  35  cm.  from  the  base.  A 
brass  tube  was  screwed  into  place,  sealed  and  connected  with  an  open- 
arm  manometer,  the  leading  tube  being  filled  with  water.  Suction 
pressures  in  terms  of  mm.  Hg.  were  recorded  as  follows  (Table  17) : 

The  tree  was  dead  at  the  time  these  observations  were  begun,  yet 
showed  two  phases  of  action  which  are  apparently  inseparable  from  a 
continuous  mesh  or  column  in  wood-cells,  viz,  daily  reversible  varia¬ 
tions  in  the  diameter  of  the  trunk  and  suction  of  a  type  indicating 
that  the  bore  penetrated  both  layers  conducting  water  and  others 
filled  with  gases.  At  the  end  the  trunk  being  progressively  desiccated, 
and  the  column  attenuated,  it  was  finally  broken.  This  stoppage 
was  coincident  with  the  work  of  beetles  and  with  a  condition  of  low 
soil  moisture. 


78 


HYDROSTATIC  SYSTEM  OF  TREES 


Table  17. 


Date. 

Time. 

Suction 

in 

mm.  Hg. 

Remarks. 

1925 

June  4 

3h05m  p.  m. 

-  0 

Clear. 

3  08  p.  m. 

-  8 

3  10  p.  m. 

-12 

3  35  p.  m. 

-25 

3  55  p.  m. 

-35 

June  5 

4  p.  m. 

-34 

Reset  to  0. 

June  6 

7  a.  m. 

-35 

4  p.  m. 

-35 

Reset  to  0;  clear  and  warm. 

June  7 

8  a.  m. 

-34 

June  8 

7  a.  m. 

-32 

Heavy  fog. 

2  p.  m. 

-30 

June  9 

7  a.  m. 

-30 

Clear. 

10  30  a.  m. 

-25 

Do. 

June  10 

7  a.  m. 

-25 

Reset;  clearing. 

3  30  p.  m. 

-21 

Clear. 

June  11 

8  a.  m. 

-27 

Cloudy. 

3  p.  m. 

-18 

Clear. 

June  12 

7  a.  m. 

-25 

Do. 

3  p.  m. 

-30 

Cloudy. 

June  13 

7  a.  m. 

-36 

Reset  to  0. 

9  a.  m. 

-  2 

Stopcock  opened. 

4  p.  m. 

. 

Stopcock  closed. 

June  14 

8  a.  m. 

-28 

Cloudy,  and  has  been  for  2  days. 

June  15 

8  a.  m. 

-33 

Cloudy. 

2  p.  m. 

-16 

Clear. 

June  16 

8  a.  m. 

-35 

Cloudy. 

4  p.  m. 

-37 

Do. 

June  17 

9  a.  m. 

-40 

Do. 

12  m. 

-33 

Do. 

4  p.  m. 

-35 

Do. 

June  18 

3  p.  m. 

-34 

Cloudy;  reset. 

June  19 

7  a.  m. 

-28 

Clear. 

11  30  a.  m. 

-28 

Clouding. 

2  30  p.  m. 

-24 

Clearing. 

June  20 

8  a.  m. 

-33 

Fog. 

June  20 

12  m. 

-33 

Fog. 

4  p.  m. 

-  0 

Do. 

June  21 

8  a.  m. 

-30 

Do. 

12  m. 

-29 

Do. 

June  22 

7  a.  m. 

-33 

Clearing. 

10  a.  m. 

-26 

Clear. 

4  p.  m. 

-16 

Do. 

June  23 

8  a.  m. 

June  24 

7  a.  m. 

-30 

Clear. 

11  a.  m. 

-27 

Do. 

2  p.  m. 

-16 

Do. 

June  25 

7  a.  m. 

-31 

Do. 

12  m. 

-30 

Do. 

4  p.  m. 

-34 

Do. 

June  26 

7  a.  m. 

-32 

Do. 

4  30  p.  m. 

-33 

Do. 

June  27 

8  a.  m. 

-34 

Cloudy. 

3  p.  m. 

-33 

Reset;  cloudy. 

June  28 

8  a.  m. 

-22 

Cloudy. 

4  p.  m. 

-24 

Warm  and  brighter. 

July  5 

8  30  a.  m. 

-32 

Overcast. 

July  8 

7  30  a.  m. 

-34 

July  12 

10  30  a.  m. 

-  0 

Clear. 

July  13 

7  30  a.  m. 

-  0 

Do. 

3  30  p.  m. 

-  1 

Tube  freshly  sealed  to  bore-hole.  Stems  showing  perfora- 

tions  by  borers. 

July  14 

7  30  a.  m. 

Action  ceased. 

CARBOHYDRATES  IN  SAP  OF  MONTEREY  PINE. 


79 


CARBOHYDRATES  IN  SAP  OF  MONTEREY  PINE. 

Earlier  determinations  based  on  extraction  from  splints  gave  marked 
differences  between  the  newest  wood  and  the  layers  beneath,  carrying 
the  sap  steam.1 

The  perfection  of  the  method  by  which  sap  was  sucked  from  the  sepa¬ 
rate  layers  gave  better  opportunity  for  determinations  of  the  sugars  as 
glucose  by  the  picric-acid  reduction  method,  as  it  had  been  previously 
used  on  the  earlier  samples. 

On  June  24  sap  drawn  from  the  current  layer  of  wood  contained 
0.27  gram  per  liter  of  sugar,  and  had  an  acidity  denoted  by  pH  5.6. 
Sap  from  the  second  and  third  layers  showed  a  sugar  content  of  0.16 
gram  per  liter,  and  pH  5.4.  The  same  layers  after  continued  extrac¬ 
tion  furnished  a  sample  with  a  sugar  content  of  0.13  gram  per  liter 
with  pH  5.5. 

Another  section  of  the  same  trunk  examined  2  days  later  yielded 
0.2  gram  per  liter  at  pH  5.4  from  the  outer  layer,  while  sap  from 
the  second  layer  showed  only  0.05  gram  per  liter  at  pH  5.6,  and  sap 
from  the  third  layer  0.07  gram  per  liter.  Sap  from  the  fourth  layer 
had  a  sugar  content  of  0.06  gram  per  liter  with  an  acidity  denoted  by 
pH  5.4  On  July  2,  a  sample  taken  from  the  outermost  layer  of  a 
small  tree  showed  0.49  gram  per  liter  and  pH  5.6.  On  July  13  and 
July  14  samples  of  sap  taken  from  the  second  and  third  layers  of  a 
small  tree  showed  a  sugar  content  of  0.28  to  0.30  gram  per  liter  at 
pH  5.4,  while  two  samples  sucked  from  the  outermost  layer  had  a 
sugar-content  of  only  0.17  gram  per  liter  at  pH  5  and  5.1. 

The  low  sugar  concentration  in  the  outermost  layer,  which  is 
the  striking  feature  of  the  last  instance,  may  be  connected  with  the  fact 
that  this  layer  is  of  a  recently  formed  internode  in  which  dye  solutions 
move  upward  with  greater  facility  than  they  do  in  wood  internal  to 
this  layer. 

Five  days  after  the  tree  was  cut  a  section  of  the  upper  end  was 
removed,  new  bores  were  made,  and  extracts  taken  from  the  outer 
layer  of  the  lower  part  of  trunk.  The  sap  of  the  outer  layer  had  a  sugar 
content  of  0.14  gram  per  liter  and  an  acidity  denoted  by  pH  6.8,  while 
the  sap  of  inner  layers  had  a  sugar  content  of  0.12  per  liter  and  an 
acidity  of  pH  5.7. 

These  meager  results  illustrate  the  fact  that  the  concentration 
of  sugar  in  the  outermost  layer  is  generally  markedly  different  from 
that  of  the  inner  wood.  The  proportion  of  sugar  is  invariably  least  in 
layers  in  which  strong  upward  movements  of  dye  take  place.  In 
accordance  with  this  idea,  sugar  is  most  concentrated  in  the  outer  layer 
of  the  lower  part  of  the  trunk,  and  least  so  in  the  terminal  internodes. 

1  MacDougal,  D.  T.  Reversible  variations  in  volume,  pressure,  and  movements  of  sap  in 
trees.  Publ.  No.  365,  Carnegie  Inst.  Wash.,  1925.  (See  pp.  30,  31,  77,  78.) 


80 


HYDROSTATIC  SYSTEM  OF  TREES. 


Fig.  17. — Manometer  with  vertical  arm  standing  in  a  dish  of  mercury,  attached  to  a 
tangential  bore  in  an  oak  tree.  Suction  =0.5  atm.  was  registered. 


The  highest  concentration  of  sugar  was  found  by  extraction  from 
cross-section  of  the  stem  in  which  communication  with  the  central 
air-filled  wood  has  been  blocked  by  a  screw  plug.  Such  a  sample 
showed  1.2  grams  sugar  per  liter  at  an  acidity  of  pH  5.6.  A  sample 
taken  from  the  second  and  third  layers  of  a  small  trunk  in  mid- 
August  yielded  9.198  grams  sugar  as  glucose,  in  6.54  liter  of  sap.  A 
lower  concentration  was  again  found  in  a  sample  from  the  second  and 
third  layers  of  a  small  trunk  taken  on  October  24,  1925,  in  which  sugar 
amounted  to  0.2  gram  per  liter  with  an  acidity  denoted  by  pH  5.5. 


SUCTION  IN  QUERCUS  AGRIFOLIA. 


81 


SUCTION  IN  QUERCUS  AGRIFOLIA. 

For  purposes  of  comparison  with  the  action  of  the  pines  one  series 
of  measurements  of  pressures  in  stems  of  Quercus  agrifolia  was  made. 
This  oak  has  a  bark  several  centimeters  in  thickness  in  which  living 
elements  persist  for  several  seasons,  and  which  does  not  begin  to 
split  or  flake  until  the  tree  has  attained  considerable  age.  The  rifts 
then  occurring  are  wide  apart.  A  bore  for  the  attachment  of  man¬ 
ometers  may  pass  through  a  layer  5  or  6  cm.  full  of  sap  before  the 
woody  cylinder  is  reached. 

The  bores  in  this  tree  were  made  tangentially  for  the  purpose 
of  engaging  the  newest  wood  in  which  the  annually  formed  layers  may 
be  a  centimeter  in  thickness.  Any  such  cavity  cuts  across  numerous 
large  vessels,  so  that  the  pressures  measured  are  to  be  taken  as  the 
complex  result  of  the  action  of  the  wood  carrying  the  sap  stream  and  of 
air-filled  conduits  into  which  water  may  pass  from  the  connecting 
tube  of  an  attached  manometer.  Operations  were  as  follows: 

May  23,  8  a.  m.  A  hole  8  mm.  in  diameter  was  bored  tangentially  in  a 
small  tree  near  the  laboratory  (fig.  17).  A  section  of  brass  tubing  threaded 
at  the  end  and  luted  with  a  thin  solution  of  Canada  balsam  was  screwed  in 
until  it  engaged  the  woody  layers  firmly  and  could  be  turned  with  difficulty. 
The  tube  engaged  the  wood  to  a  depth  of  15  mm.,  and  a  cavity  4.5  cm.  was 
left  free.  A  manometer  with  an  open  arm  was  attached  (fig.  3),  to  be  re¬ 
placed  later  by  the  vertical  column  shown  in  figure  17.  The  stopcock  of  the 
manometer  was  left  open  to  allow  absorption  of  water  by  the  trunk  for  a  few 
hours.  The  records  are  shown  in  Table  18. 


82 


HYDROSTATIC  SYSTEM  OF  TREES. 


Table  18. 


Date. 

Time. 

Suction 

in 

mm.  Hg. 

Remarks. 

1925 

May  23 

8h10m  a.  m. 

. 

20  ml.  water  absorbed. 

8  22  a.  m. 

•  •••••••• 

15  ml.  water  absorbed. 

8  38  a.  m. 

«•••••••• 

20  ml.  wTater  absorbed. 

11  30  a.  m. 

......... 

30  ml.  water  absorbed.  After  about  100  ml.  water  had 

entered  the  wood,  the  stopcock  was  closed  and  further 

absorptions  were  recorded  as  suction  in  terms  of 

mm.  Hg. 

11  40  a.  m. 

......... 

Set  at  0. 

11  42  a.  m. 

-  48 

11  50  a.  m. 

-  75 

May  24 

9  10  a.  m. 

Open  from  previous  record.  Set  at  0. 

10  a.  m. 

-  20 

10  30  a.  m. 

-  38 

May  25 

8  a.  m. 

-  12 

4  p.  m. 

-  12 

May  26 

8  a.  m. 

-  12 

Cloudy. 

11  30  a.  m. 

-  11 

Sunny. 

May  27 

9  a.  m. 

-  12 

3  p.  m. 

-  12 

May  28 

8  a.  m. 

-  12 

May  30 

12  m. 

Reset  at  0. 

2  p.  m. 

-  12 

4  p.  m. 

-  12 

May  31 

8  30  a.  m. 

-  12 

Raining. 

11  a.  m. 

-  15 

Clearing. 

5  30  p.  m. 

-  20 

June  1 

7  a.  m. 

-  20 

Reset  at  0;  raining. 

4  p.  m. 

-  18 

Clear. 

June  2 

8  a.  m. 

-  26 

Raining. 

12  m. 

-  36 

Cloudy. 

4  p.  m. 

-  50 

Raining. 

June  3 

8  a.  m. 

-  55 

Clearing. 

4  p.  m. 

-  74 

Clear. 

June  4 

8  a.  m. 

-  78 

Clear. 

11  30  a.  m. 

-  80 

Do. 

3  30  p.  m. 

-  77 

Do. 

June  5 

7  a.  m. 

-  44 

Raining. 

4  p.  m. 

-  60 

June  6 

7  a.  m. 

-  65 

Cloudy. 

4  p.  m. 

-  58 

Clear. 

June  7 

8  a.  m. 

-  48 

June  8 

7  a.  m. 

-  30 

2  p.  m. 

-  32 

June  9 

7  a.  m. 

-  55 

Clear.  Reset;  a  large  air-bubble  released. 

7  30  a.  m. 

......... 

8  10  a.  m. 

-  5 

10  30  a.  m. 

-  6 

June  10 

3  30  p.  m. 

-  10 

June  11 

8  a.  m. 

-  6 

Cloudy. 

3  p.  m. 

-  11 

Clear. 

June  12 

7  a.  m. 

-  17 

Do. 

3  p.  m. 

-  36 

Cloudy. 

June  13 

7  a.  m. 

-  44 

Do. 

9  a.  m. 

-  52 

Do. 

4  p.  m. 

—  65 

Do. 

June  14 

8  a.  m. 

-  80 

Do. 

9  a.  m. 

-  80 

Do. 

June  15 

8  a.  m. 

-112 

Do. 

2  p.  m. 

-  70 

Clear.  Air;  reset  to  0. 

June  16 

8  a.  m. 

-  2 

Cloudy. 

4  p.  m. 

-  9 

Do. 

SUCTION  IN  QUERCUS  AGRIFOLIA 


83 


Table  18. — Continued. 


Date. 

Time. 

Suction 

in 

mm.  Hg. 

1 

Remarks. 

1925 

June  17 

9h  m  a.  m. 

-  10 

Cloudy. 

12  m. 

-  11 

Do. 

4  p.  m. 

-  20 

Do. 

June  18 

3  p.  m. 

-  32 

Do. 

June  19 

7  a.  m. 

-  39 

Clear. 

9  30  a.  m. 

-  42 

Do. 

11  30  a.  m. 

-  53 

Clouding. 

2  30  p.  m. 

-  60 

Clearing. 

June  20 

8  a.  m. 

-  75 

Fog. 

12  m. 

-  70 

Do. 

4  p.  m. 

-  83 

Do. 

June  21 

8  a.  m. 

-  96 

Do. 

12  m. 

-  98 

Do. 

June  22 

7  a.  m. 

-122 

Clearing. 

8  30  a.  m. 

-132 

Clear. 

10  a.  m. 

-134 

Do. 

4  p.  m. 

-141 

Do. 

June  23 

8  a.  m. 

-139 

Do. 

10  30  a.  m. 

-120 

Do. 

June  24 

7  a.  m. 

-168 

Do. 

11  a.  m. 

-168 

Do. 

2  p.  m. 

204 

Manometer  replaced  by  vertical  column  (fig.  15). 

June  25 

7  a.  m. 

-  23 

Clear. 

12  m. 

-  70 

Do. 

4  p.  m. 

-102 

Do. 

June  26 

7  a.  m. 

-115 

Do. 

4  30  p.  m. 

-190 

Do. 

June  27 

8  a.  m. 

-175 

Cloudy. 

3  p.  m. 

-185 

Do. 

June  28 

8  a.  m. 

-182 

Cloudy. 

4  p.  m. 

-208 

Do. 

June  29 

9  a.  m. 

-200 

Do. 

4  p.  m. 

-215 

Do. 

June  30 

7  a.  m. 

-200 

Clear.  Air  bubble  released;  reset  to  —200. 

2  p.  m. 

-235 

Clear. 

July  1 

7  a.  m. 

-215 

Do. 

8  a.  m. 

-220 

Do. 

9  a.  m. 

-221 

Do. 

10  a.  m. 

-225 

Do. 

11  a.  m. 

-236 

Do. 

12  m. 

-235 

Do. 

3  p.  m. 

-245 

Fog. 

4  30  p.  m. 

-246 

Do. 

8  p.  m. 

-245 

Do. 

July  2 

7  a.  m. 

-233 

Do. 

8  a.  m. 

-225 

Fog  and  drizzle;  air  released;  reset  to  —170. 

9  30  p.  m. 

•  •••••••• 

Air  released;  reset  to  —160. 

11  a.  m. 

-158 

Misty. 

7  p.  m. 

-168 

Do. 

July  3 

7  a.  m. 

-177 

Do. 

8  30  a.  m. 

-160 

Do. 

11  30  a.  m. 

-165 

Clearing. 

2  30  p.  m. 

-175 

Do. 

5  p.  m. 

-185 

Fog. 

July  4 

9  a.  m. 

-176 

Do. 

11  a.  m. 

-180 

Clear. 

3  30  a.  m. 

-240 

Do. 

July  5 

8  30  a.  m. 

-196 

Overcast. 

10  30  a.  m. 

-200 

Clear. 

4  30  p.  m. 

-234 

Do. 

84 


HYDROSTATIC  SYSTEM  OF  TREES 


Table  18. — Continued. 


Date. 

Time. 

Suction 

in 

mm.  Hg. 

Remarks. 

1925 

July 

6 

7h 

m 

a.  m. 

-246 

Clear. 

11 

a.  m. 

Air  released;  reset  at  —190. 

6 

30 

p.  m. 

-246 

Clear. 

July 

7 

7 

a.  m. 

-220 

Do. 

9 

a.  m. 

-220 

Do. 

2 

p.  m. 

-228 

Do. 

4 

p.  m. 

-238 

Do. 

July 

8 

7 

30 

a.  m. 

-220 

Large  air  bubble  released;  set  to  —224. 

9 

30 

a.  m. 

-224 

Clearing. 

2 

p.  m. 

-262 

Clearing.  Air  in  tube  released,  reset  to  —258. 

4 

p.  m. 

-268 

Overcast. 

July 

9 

7 

30 

a.  m. 

-233 

Fog  and  drizzle. 

10 

30 

a.  m. 

-226 

Do. 

4 

p.  m. 

-235 

Overcast. 

July 

11 

7 

30 

a.  m. 

-218 

Clear. 

11 

a.  m. 

-180 

Air  out;  set  at  —170.  Clear. 

2 

30 

p.  m. 

-188 

Clear. 

4 

30 

p.  rn. 

-250 

Do. 

July 

12 

8 

a.  m. 

-223 

Do. 

10 

30 

a.  m. 

-233 

Do. 

July 

13 

7 

30 

a.  m. 

-243 

Do. 

9 

30 

a.  m. 

-254 

Do, 

12 

m. 

-263 

Do. 

3 

30 

p.  m. 

-272 

Air  out;  reset  at  —248. 

July 

14 

7 

30 

a.  m. 

-235 

Clear, 

11 

30 

a.  m. 

-242 

Clouds. 

2 

15 

p.  m. 

-268 

Foggy. 

July 

15 

7 

30 

a.  m. 

-240 

Foggy. 

9 

30 

a.  m. 

-238 

Clear.  Air  released;  reset  at  —235. 

1 

30 

p.  m. 

—255 

July 

16 

7 

a.  m. 

-233 

Clear. 

11 

a.  m. 

-236 

Do. 

3 

30 

p.  m. 

-260 

Do. 

July 

17 

7 

a.  m. 

-230 

Do. 

3 

15 

p.  m. 

-262 

July 

18 

7 

a.  m. 

-233 

Clouds.  Air  released  and  reset  to  235. 

July 

19 

7 

40 

a.  m. 

-232 

Air  out;  reset  to  —205. 

8 

a.  m. 

-230 

Clouds. 

11 

30 

a.  m. 

-250 

4 

p.  m. 

-262 

5 

p.  m. 

-238 

July 

20 

7 

a.  m. 

-222 

Cloudy. 

11 

30 

a.  in. 

-218 

3 

30 

p.  m. 

-238 

Clear. 

July 

21 

7 

a.  m. 

-230 

Overcast. 

11 

a.  m. 

-278 

Do. 

4 

p.  m. 

-248 

Clouds. 

July 

22 

7 

a.  m. 

-238 

Air  out;  reset  at  —220. 

4 

30 

p.  m. 

-240 

July 

23 

7 

40 

a.  m. 

-220 

Overcast. 

11 

45 

a.  m. 

-238 

Clear. 

4 

p.  m. 

-260 

Air  out;  reset  at  —270.  Clear. 

July 

24 

7 

30 

a.  m. 

-  98 

Cloudy.  Air  released;  reset  at  —200. 

4 

p.  m. 

-222 

Clouds. 

July 

25 

7 

30 

a.  m. 

-220 

Overcast. 

9 

a.  m. 

-226 

Clear. 

12 

m. 

-220 

Do. 

3 

p.  m. 

-235 

Clouds. 

July 

26 

7 

30 

a.  m. 

-218 

Fog.  Air  released;  reset  at  —210. 

10 

a.  m. 

-208 

Overcast. 

3 

p.  m. 

-225 

Do. 

SUCTION  IN  QUERCUS  AGRIFOLIA. 


85 


Table  IS. — Continued. 


Date. 

Time. 

Suction 

in 

mm.  Hg. 

Remarks. 

1925 

July 

27 

7h30m 

a.  m. 

-206 

Overcast. 

11 

30 

a.  m. 

-205 

Do. 

2 

30 

p.  m. 

-210 

Do. 

July 

28 

7 

a.  m. 

-202 

Overcast.  Air  released;  reset  at  —210. 

11 

a.  m. 

Reset  at  —200. 

2 

p.  m. 

-170 

July 

29 

7 

40 

a.  m. 

•  •••••••• 

Instrument  leaking  at  stopcocks. 

July 

31 

7 

30 

a.  m. 

•  •••••••a 

Refitted  and  reset  at  —180. 

11 

30 

a.  m. 

-176 

Sunny. 

Aug. 

2 

3 

45 

p.  m. 

-175 

Do. 

Aug. 

3 

7 

30 

a.  m. 

-178 

Overcast. 

11 

30 

a.  m. 

-176 

Sunshine. 

3 

40 

p.  m. 

-177 

Do. 

Aug. 

4 

8 

a.  m. 

-175 

Overcast. 

2 

30 

p.  rn. 

-175 

Sunny. 

Aug. 

5 

9 

a.  m. 

-176 

Fog. 

Aug. 

6 

2 

30 

p.  m. 

-171 

Sunshine. 

Aug. 

7 

9 

a.  m. 

-173 

Fog. 

4 

p.  m. 

-170 

Sunny.  Opened  to  absorb  water. 

Aug. 

8 

4 

p.  m. 

•  •••••••a 

2.8  ml.  absorbed. 

Aug. 

9 

7 

p.  m. 

......... 

2.5  ml.  absorbed. 

Aug. 

10 

4 

p.  m. 

......... 

2.  Stopcocks  closed  and  column  set  to  —170. 

Aug. 

11 

8 

a.  m. 

-223 

Clear. 

11 

30 

a.  m. 

-240 

Do. 

7 

p.  m. 

-272 

Do. 

Aug. 

12 

7 

30 

a.  m. 

-260 

Do. 

11 

30 

a.  m. 

-270 

Do. 

4 

15 

p.  m. 

-303 

Do. 

Aug. 

13 

7 

30 

a.  m. 

-288 

Overcast. 

11 

30 

a.  m. 

-290 

Do. 

7 

p.  m. 

-318 

Clear  afternoon. 

Aug. 

14 

5 

45 

a.  m. 

-305 

Overcast. 

8 

45 

a.  in. 

-300 

Clearing. 

Aug. 

15 

11 

a.  m. 

-307 

Overcast.  Air  released;  reset  at  —295. 

Aug. 

16 

7 

30 

a.  m. 

-290 

Do. 

4 

p.  m. 

-305 

Do. 

Aug. 

17 

7 

30 

a.  m. 

-295 

Do. 

11 

30 

a.  m. 

-302 

Clear  at  9h30m. 

4 

30 

p.  m. 

-320 

Do. 

Aug. 

18 

7 

30 

a.  m. 

-340 

Do. 

11 

a.  m. 

-305 

Air  out;  reset  at  —308. 

4 

p.  m. 

-325 

Aug. 

19 

7 

a.  m. 

-358 

Clear. 

11 

45 

a.  m. 

-320 

Do. 

4 

15 

p.  m. 

-380 

Do. 

Aug. 

20 

7 

30 

a.  m. 

-314 

Overcast. 

11 

30 

a.  m. 

-343 

Clear. 

Aug. 

21 

3 

30 

p.  m. 

-325 

Do. 

Aug. 

22 

8 

a.  m. 

-317 

Do. 

11 

30 

a.  m. 

-320 

Do. 

5 

p.  m. 

-333 

Do. 

Aug. 

23 

8 

a.  m. 

-325 

Misting. 

11 

15 

a.  m. 

-323 

Clearing. 

4 

30 

p.  m. 

-328 

Air  out;  reset  at  —308. 

Aug. 

24 

7 

30 

a.  m. 

-310 

Column  fell  10  mm.  to  this  point  on  shaking  slightly. 

Clear. 

11 

30 

a.  m. 

-318 

Clear. 

4 

p.  rn. 

-332 

Do. 

Aug. 

25 

7 

30 

a.  m. 

-333 

Do. 

11 

30 

a.  m. 

-333 

Do. 

4 

p.  m. 

-338 

Do. 

86 


HYDROSTATIC  SYSTEM  OF  TREES. 


Table  18. — Continued. 


Date. 

Time. 

Suction 

in 

mm.  Hg. 

Remarks. 

1925 

Aug.  26 

8h 

m 

a.  m. 

-321 

Air  released;  reset  at  —307.  Overcast. 

11 

30 

a.  m. 

-297 

Beginning  to  clear. 

7 

15 

p.  m. 

-305 

Overcast. 

Aug.  27 

6 

a.  m. 

-293 

7 

a.  m. 

-292 

8 

a.  m. 

-289 

9 

a.  m. 

-288 

10 

a.  m. 

-288 

12 

m. 

-296 

2 

p.  m. 

-299 

3 

p.  m. 

-302 

4 

p.  m. 

-303 

5 

p.  m. 

-304 

8 

p.  m. 

-304 

11 

p.  m. 

-300 

Aug.  28 

3 

a.  m. 

-299 

4 

a.  m. 

-298 

1 

6 

a.  m. 

-297 

8 

a.  m. 

-296 

9 

a.  m. 

-294 

10 

a.  m. 

-295 

11 

a.  m. 

-296 

2 

p.  m. 

-301 

4 

p.  m. 

-304 

7 

p.  m. 

-308 

9 

p.  m. 

-306 

Aug.  29 

3 

a.  m. 

-304 

4 

a.  m. 

-302 

6 

a.  m. 

-304 

8 

a.  m. 

-297 

Aug.  30 

9 

a.  m. 

-289 

Air  released;  reset  at  —290. 

10 

a.  m. 

-290 

12 

m. 

-280 

Clear. 

6 

p.  m. 

-282 

Do. 

Aug.  31 

9 

a.  m. 

-275 

Overcast. 

4 

p.  m. 

-287 

Do. 

Sept.  1 

7 

a.  m. 

•  •••••••• 

12 

m. 

-288 

Clear. 

7 

p.  m. 

-297 

Do. 

Sept.  2 

7 

a.  m. 

-296 

11 

a.  m. 

-295 

Sept.  5 

11 

a.  m. 

-300 

6 

30 

p.  m. 

-308 

Sept.  6 

8 

30 

a.  m. 

-301 

Clearing. 

6 

p.  m. 

-297 

Clouds. 

Sept.  7 

7 

30 

a.  m. 

-298 

Clear. 

11 

15 

a.  m. 

-293 

Do. 

4 

15 

p.  m. 

-297 

Sept.  8 

7 

30 

a.  m. 

-297 

Do. 

11 

30 

a.  m. 

-288 

Do. 

4 

p.  m. 

-293 

Sept.  9 

8 

a.  m. 

-295 

Cloudy. 

11 

30 

a.  m. 

-293 

Clear. 

Sept.  10 

7 

30 

a.  m. 

-287 

Cloudy. 

Sept.  13 

8 

a.  m. 

-263 

Air  released  and  reset  at  —340. 

6 

p.  m. 

-333 

Clear. 

Sept.  14 

7 

15 

a.  m. 

-333 

Do. 

11 

30 

a.  m. 

-322 

Do. 

4 

p.  m. 

-317 

Do. 

Sept.  15 

7 

15 

a.  m. 

-293 

Do. 

3 

30 

p.  m. 

-282 

Do. 

SUCTION  IN  QUERCUS  AGRIFOLIA 


87 


Table  18. — Continued. 


Date. 

Time. 

Suction 

in 

mm.  Hg. 

Remarks. 

1925 

Sept.  16 

7h30m  a.  m. 

-256 

Clouds. 

Sept.  18 

7  a.  m. 

-200 

Clouds;  rain  on  Sept.  17. 

Sept.  20 

9  a.  m. 

-193 

Clear. 

Sept.  21 

7  30  a.  m. 

-195 

Do. 

11  30  a.  m. 

-193 

Do. 

4  p.  m. 

-188 

Clear. 

5  p.  m. 

•  •••••••• 

Sept.  22 

7  30  a.  m. 

-193 

Do. 

11  30  a.  m. 

-189 

Do. 

5  30  p.  m. 

-191 

Cloudy. 

Sept.  23 

8  a.  m. 

-197 

Do. 

12  m. 

-190 

4  p.  m. 

-187 

Sept.  24 

7  15  a.  m. 

-195 

Overcast. 

11  30  a.  m. 

-184 

Clearing. 

4  p.  m. 

-182 

Clouds. 

Sept.  25 

8  a.  m. 

-183 

Clear. 

5  p.  m. 

-178 

Do. 

Sept.  26 

7  15  a.  m. 

-186 

Do. 

11  45  a.  m. 

-178 

Do. 

4  p.  m. 

-174 

Sept.  28 

7  30  a.  m. 

-178 

Some  clouds. 

Sept.  29 

9  45  a.  m. 

-183 

Clear. 

Sept.  30 

4  p.  m. 

-167 

Do. 

Oct.  4 

9  a.  m. 

-160 

Do. 

4  p.  m. 

-158 

Do. 

Oct.  5 

7  30  a.  m. 

-172 

Clear.  Fittings  imperfect.  Apparatus  dismounted, 

cleaned  and  refitted;  column  reset  at  —227. 

Oct.  8 

11  a.  m. 

-183 

No  air  in  tube. 

4  p.  m. 

-175 

Clear. 

Oct.  9 

7  30  a.  m. 

-177 

Cloudy. 

3  30  p.  m. 

-165 

Do. 

Oct.  10 

8  a.  m. 

-150 

Do. 

12  m. 

-144 

Overcast. 

4  p.  m. 

-138 

Do. 

Oct.  11 

8  15  a.  m. 

-120 

No  air  drawn  in  by  this  drop  from  —183. 

Oct.  12 

8  a.  m. 

-102 

Rainy  since  noon  of  Oct.  11. 

4  p.  m. 

-  95 

Clouds. 

Oct.  13 

8  a.  m. 

-  97 

Clear. 

2  p.  m. 

-  85 

Oct.  14 

8  a.  m. 

-  86 

Do. 

Oct.  16 

9  a.  m. 

-  67 

4  p.  m. 

-  64 

Oct.  17 

8  a.  m. 

-  62 

Oct.  18 

9  a.  m. 

-  63 

Oct.  19 

8  a.  m. 

-  63 

4  p.  m. 

-  56 

Oct.  20 

9  a.  m. 

-  72 

2  p.  m. 

-  65 

Oct.  21 

8  a.  m. 

-  80 

Oct.  22 

4  p.  m. 

-  93 

Oct.  23 

7  a.  m. 

-102 

11  a.  m. 

-  99 

Oct.  24 

7  a.  m. 

-108 

12  m. 

-106 

7  p.  m. 

-100 

Oct.  25 

8  a.  m. 

-110 

Clear. 

Oct.  26 

7  30  a.  m. 

-210 

Do. 

Oct.  27 

8  a.  m. 

-133 

Overcast. 

4  p.  m. 

-126 

Clear. 

88 


HYDROSTATIC  SYSTEM  OF  TREES 


Table  18. — Continued. 


Date. 

Time. 

Suction 

in 

mm.  Hg. 

Remarks. 

1925 

Oct.  28 

7h30m  a.  m. 

-136 

Overcast. 

4  p.  m. 

-133 

Do. 

Oct.  29 

2  p.  m. 

-133 

Clear. 

Oct.  30 

7  30  a.  m. 

-142 

Overcast. 

Oct.  31 

8  a.  m. 

-143 

Do. 

Nov.  1 

10  30  a.  m. 

-151 

Do. 

Nov.  2 

8  a.  m. 

-158 

Showers. 

Nov.  3 

9  a.  m. 

-165 

Clearing. 

Nov.  4 

8  a.  m. 

-156 

Clear. 

4  p.  m. 

-148 

Do. 

Nov.  5 

8  a.  m. 

-155 

Do. 

4  p.  m. 

-146 

Do. 

Nov.  6 

8  a.  m. 

-154 

Do. 

3  p.  m. 

-142 

No  air  had  been  drawn  out  accompanying  lessened  sue- 

tion  from  Oct.  8-20,  when  suction  began  to  increase. 

Nov.  7 

8  a.  m. 

-147 

Nov.  8 

10  a.  m. 

-134 

Nov.  9 

8  a.  m. 

-137 

Clear. 

3  p.  m. 

-128 

Cloudy. 

Nov.  10 

4  p.  m. 

-124 

Do. 

Nov.  11 

7  30  a.  m. 

-123 

Raining. 

4  p.  m. 

-118 

Do. 

Nov.  12 

8  a.  m. 

-120 

Cloudy. 

4  p.  m. 

-110 

Raining. 

Nov.  13 

7  30  a.  m. 

-114 

Clear. 

Nov.  14 

7  30  a.  m. 

-128 

Do. 

4  p.  m. 

-104 

Do. 

Nov.  15 

8  a.  m. 

-110 

Do. 

1  30  p.  m. 

-  96 

Do. 

4  p.  m. 

-101 

Cloudy. 

Nov.  16 

8  a.  m. 

-  97 

Drizzle. 

Nov.  17 

7  30  a.  m. 

-  99 

Clear. 

Nov.  18 

7  30  a.  m. 

-  96 

Do. 

11  30  a.  m. 

-  93 

Do. 

2  p.  m. 

-  84 

Do. 

7  p.  m. 

-  90 

Do. 

Nov.  19 

7  30  a.  m. 

-  91 

Do. 

Nov.  20 

8  a.  m. 

-  95 

Do. 

11  30  a.  m. 

-  82 

Do. 

2  p.  m. 

-  79 

Do. 

4  30  p.  m. 

-  86 

Do. 

Nov.  21 

8  a.  m. 

-  97 

Overcast. 

12  m. 

-  88 

Slightly  overcast. 

4  p.  m. 

-  88 

Overcast. 

Nov.  22 

8  a.  m. 

-105 

Clear. 

Nov.  23 

7  30  a.  m. 

-  99 

Overcast. 

Nov.  24 

7  30  a.  m. 

-105 

Do. 

2  p.  m. 

-100 

Clear. 

Nov.  25 

7  a.  m. 

-121 

Do. 

2  p.  m. 

-109 

Hazy. 

Nov.  26 

12  m. 

-110 

Do. 

Nov.  27 

8  a.  m. 

-127 

Clear. 

Nov.  28 

8  a.  m. 

-128 

Do. 

SUCTION  AND  CONDUCTION  OF  DYE  IN  SMALL  OAK  TREE.  89 


SUCTION  AND  CONDUCTION  OF  DYE  IN  SMALL  OAK  TREE. 

The  extent  of  absorption  of  liquid  from  a  bore-hole  in  the  trunk, 
and  the  capillary  conduction  of  such  liquid,  was  tested  by  experiments 
with  small  oak  trees,  using  a  solution  of  acid  fuchsin  1-1,000  in  water 
in  the  cavity. 

The  first  tree  tested  had  a  diameter  of  about  10  cm.,  and  a  height 
of  3  meters.  A  manometer  with  open  U  tube  adjusted  at  8  a.  m. 
showed  a  suction  of  —  42  mm.  Hg.  by  llh20m  a.  m.  At  8  a.  m. 
of  the  following  day,  the  dye  had  gone  down  the  trunk  60  cm.  and  up¬ 
ward  90  cm.  in  the  vessels  of  the  third,  fourth  and  fifth  layers  (fig.  16). 
About  3  ml.  of  gas  had  been  displaced  and  accumulated  in  the  man¬ 
ometer.  A  similar  bore  in  a  second  tree,  connected  with  a  manometer 
at  once,  at  8h20m  a.  m.  showed  suction  of  —40  mm.  Hg. ;  by  9h30rn  a.  m., 
with  displacement  of  3  ml.  gas;  at  10  a.  m.  2  ml.  gas  had  been  displaced 
and  a  suction  of  —42  set  up,  the  instrument  having  been  reset  to  0. 
A  similar  record  was  made  at  llh15m  a.  m.  At  4  p.  m.,  suction  of 
—  25  mm.  was  shown  with  an  accumulation  of  25  ml.  gas.  At  4h40m 
p.  m.  another  record  of  —84  mm.  Hg.  with  displacement  of  2  ml.  of 
gas  was  made.  The  dye  had  gone  down  the  trunk  65  cm.  and  upward 
100  cm.  by  the  following  morning  in  a  total  of  26  hours.  A  bore  in  a 
third  small  tree  yielded  the  following  records: 


Table  19. 


Date. 

Time. 

Suction 

in 

mm.  Hg. 

Remarks. 

1925 
Sept.  26 

llh  m  a.  m. 

Manometer  fitted. 

11  30  a.  m. 

-  70 

No  air. 

3  p.  m. 

3  40  p.  m. 

-  42 

-  67 

1  ml.  air  released;  reset  to  0. 

No  air. 

Sept.  27 

4  p.  m. 

7  30  a.  m. 

-  86 
-  8 

Do. 

15  ml.  air  released;  reset  at  0. 

11  a.  m. 

4  p.  m. 

-  33 
-102 

2  ml. ;  air  released. 

2  ml.;  air  released;  reset  to  0.  Not  read  for  2  weeks. 

The  bore  in  this  tree  cut  across  a  number  of  large  conduits,  which 
must  have  contained  gas  as  an  amount  of  water  estimated  at  150  ml. 
was  taken  from  the  bore  by  capillarity  in  the  first  w^eek  of  the  test. 
In  this  as  in  many  other  preparations  suction  increased  throughout 
the  day,  and  a  progressive  increase  would  follow  every  release  of 
the  column  by  which  it  was  set  at  0.  Thus  when  the  column  was  set 
at  0  on  May  15,  it  rose  irregularly  to  —204  mm.  Hg.  =  0.26  atm.  on 
the  24th.  Being  again  reset,  suction  increased  to  —225  mm.  =  0.28 
atm.  on  June  2.  After  this  time  a  mid-day  decrease  of  suction  was 
observed,  or  if  a  general  increase  were  in  progress  a  slacking  off  of  the 
rate  was  noticeable. 

Disturbances  of  the  weather,  fog,  clouds,  etc.,  in  which  a  daily  rise 
in  temperature  was  modified,  would  be  followed  by  deviations  from 


90 


HYDROSTATIC  SYSTEM  OF  TREES. 


this  program  in  which  changes  in  volume  of  included  gases  was  the 
determining  factor.  Gases  were  drawn  out  in  much  greater  quantity 
than  in  the  walnut  or  pine.  The  maxima  of  suction  observed  in¬ 
creased  until  August  20,  when  a  reading  of  —380  mm.  Hg.  =0.5  atm. 
was  made.  Deducting  a  fraction  for  capillary  action  this  may  be 


Fig.  18. — Diagrams  of  longitudinal  and  cross  sections  of  small  oak  tree  ( Quercus  agrifolia) 
showing  capillary  conduction  of  dye  from  a  tangential  bore.  D,  penetration  of  bore; 

A,  conduction  of  dye  downward  and  upward  in  trunk  shown  by  shading.  Stained 
wood  near  bore  and  above  it  shown  by  shading  in  cross-sections  B  and  C. 

taken  as  an  index  of  pressure  in  the  included  gases  notably  less  than 
atmospheric,  and  as  the  extreme  in  the  season’s  observations. 

After  a  period  of  suction  little  below  the  maximum,  a  diminution 
followed,  so  that  during  the  latter  half  of  November  suction  varied 
below  and  above  —100  mm.  Hg. 


SUCTION  AND  CONDUCTION  OF  DYE  IN  SMALL  OAK  TREE.  91 


Table  20. 


Date. 

Time. 

Suction  in 
mm.  Hg. 

Date. 

Time. 

Suction  in 
mm.  Hg. 

1925 

1925 

Oct. 

11 

8h00m 

a. 

m. 1 

-108 

Oct. 

24 

7h 

m 

P- 

m. 

-222 

Oct. 

12 

4 

P- 

m. 

-  95 

Oct. 

25 

8 

a. 

m. 

-228 

Oct. 

13 

8 

a. 

m. 

-  86 

Oct. 

26 

7 

30 

a. 

m. 

-148 

2 

p. 

m. 

-  18 

Oct. 

27 

8 

a. 

m. 

-138 

Oct. 

14 

8 

a. 

m. 

-  72 

4 

P- 

m. 

-122 

Oct. 

16 

9  . 

a. 

m. 

-140 

Oct. 

28 

7 

30 

a. 

m. 

-121 

4 

P- 

m. 

-  35 

Oct. 

29 

2 

P- 

m. 

-114 

Oct. 

17 

8 

a. 

m. 

-  92 

Oct. 

30 

7 

30 

a. 

m.2 

-105 

Oct. 

18 

9 

a. 

m. 

-  88 

Oct. 

31 

8 

a. 

m. 

-  86 

Oct. 

19 

8 

a. 

m. 

-140 

Nov. 

1 

10 

a. 

m. 

-  90 

Oct. 

20 

9 

a. 

m. 

-177 

Nov. 

2 

8 

a. 

m. 

-  96 

2 

P- 

m. 

-186 

Nov. 

3 

9 

a. 

m. 

-101 

Oct. 

21 

8 

a. 

m. 

-204 

Nov. 

4 

8 

a. 

m. 

-102 

Oct. 

22 

4 

P- 

m. 

-204 

4 

P- 

m. 

-  99 

Oct. 

23 

7 

a. 

m. 

-220 

Nov. 

5 

8 

a. 

m. 

-109 

11 

a. 

m. 

-210 

4 

P- 

m. 

-106 

Oct. 

24 

7 

a. 

m. 

-228 

Nov. 

6 

8 

a. 

m.3 

-111 

12 

m. . 

-175 

4 

p. 

m. 

-106 

1  1  ml.  air  released;  reset  to  0. 

2  Air  released;  reset  at  —65. 

*  No  air  had  been  displaced  since  Oct.  30. 


The  tree  was  now  taken  down.  The  bore  had  actually  penetrated 
about  2  cm.  radially  to  within  a  centimeter  of  the  center.  The  dye 
was  visible  to  a  distance  of  only  30  cm.  below  the  cavity  and  twice  as 
far  above  it  in  a  sector  not  noticeably  wider  than  the  bore.  The 
larger  vessels  were  plainly  filled,  while  wood  cells  and  living  elements 
enmeshed  with  them  were  uncolored.  It  was  plainly  obvious  that 
the  liquid  in  the  manometer  system  was  continuous  with  capillary 
extensions  into  the  larger  vessels  from  which  gases  had  been  displaced 
to  the  lengths  indicated.  Wide  fluctuations  in  the  suction  took  place 
in  the  month  ending  November  6,  when  the  experiment  was  terminated. 
The  maximum  was  reached  during  the  period  of  October  21  to  25, 
when  the  outer  layers  of  other  trees  nearby  were  showing  temper¬ 
atures  of  19°  to  24°  C.  in  the  outer  layers.  The  lower  suction  force 
measured  October  28  to  November  6  was  coincidental  with  measuring 
stem  temperatures  as  low  as  5°  C.  at  7  to  8  a.  m. 

Suction  is  seen  to  increase  during  periods  in  which  the  temperature 
of  the  stem  runs  higher  from  day  to  day  with  implied  increase  of 
water  loss,  and  it  would  appear  that  the  last-named  factor  is  the 
one  to  be  connected  directly  with  the  force  of  suction  developed. 

An  analysis  of  the  daily  variations,  which  are  generally  similar  to 
the  variations  in  suction  of  the  central  cylinder  of  both  the  pine  and 
the  walnut,  is  not  so  easily  made. 

Suction  is  greatest  about  the  beginning  of  the  daylight  period  at 
the  time  when  the  trunk  has  reached  the  limit  of  its  daily  expansion 
and  the  outer  layers  are  near  the  minimum  temperature  with  a  mini- 


92 


HYDROSTATIC  SYSTEM  OF  TREES. 


mum  rate  of  water-loss.  Suction  force  now  decreases  toward  mid¬ 
day  and  begins  to  rise  again  late  in  the  afternoon.  This  is  well  illus¬ 
trated  by  the  observations  of  October  24,  on  which  date  suction 
amounted  to  228  mm.  Hg.  at  7  a.  m.  with  temperature  of  trunks  at 
14°  C.;  fell  to  175  mm.  at  noon,  with  trunk  temperature  at  24°  C.; 
and  had  risen  to  222  mm.  at  7  p.  m.  wTith  trunk  temperature  at  15°  C. 
The  decrease  in  suction  may  be  due  in  part  to  expansion  of  gases  in 
the  wood,  coupled  with  the  actual  contraction  of  the  stem.  These 
factors  are  mentioned  as  the  only  ones  the  action  of  which  is  at  all 
concurrent  with  the  variations  in  suction. 

The  extensive  series  of  measurements  in  the  larger  oak  tree, 
described  in  the  previous  section,  was  made  by  instruments  attached 
to  bores  driven  tangentially  into  the  trunk  and,  therefore,  engaging 
more  or  less  fully  with  the  ascending  sap  stream,  in  which  other  factors 
would  be  dominant  in  the  determination  of  daily  variations. 

COMPOSITION  OF  GASES  IN  CENTRAL  CYLINDER  OF 

TRUNK  OF  OAK. 

The  composition  of  the  gases  in  the  central  part  of  tree-trunks  is  a 
matter  of  importance  in  several  ways,  and  analyses  were  made  of 
samples  from  the  pine  and  the  walnut.  The  sample  of  gases  from  the 
oak  was  taken  from  a  tree  about  30  cm.  in  diameter,  standing  near  the 
one  to  which  the  manometer  had  been  attached  for  several  months. 
A  bore  was  driven  radially  into  the  trunk  to  depth  of  12  cm.,  a  brass 
tube  screwed  into  the  opening  and  a  luting  of  stiff  grease  applied.  A 
gas  receiver  (fig.  16)  connected  with  a  column  of  mercury  for  exhausting 
was  fitted.  The  preparation  was  fitted  October  6  at  3h30m  p.  m., 
and  the  system,  put  under  suction  of  a  column  of  mercury  300  mm., 
was  arranged  to  clear  it  of  atmospheric  gases.  The  column  was  again 
set  as  above  and  about  30  ml.  gas  drawn  out  in  the  first  half  hour. 
The  suction  given  above  was  allowed  to  act  until  9  a.  m.  the  following 
morning.  About  200  ml.  gas  was  drawn  out  in  the  intervening  17 
hours.  This  was  found  by  two  analyses  to  have  a  composition  as 
below:  C02:  3.08  p.  ct. ;  3.04  p.  ct.  Oxygen:  17.84  p.  ct. ;  17.49  p.  ct. 
N:  79.08  p.  ct.;  79.47  p.  ct. 

The  receiver  was  again  attached  at  10h30m  a.  m.,  and  a  suction  of 
about  200  mm.  Hg.  arranged.  22  hours  later  over  200  ml.  gas  had 
been  obtained,  which  had  a  composition  as  below:  C02:  3.4  p.  ct. ; 
3.43  p.  ct.  Oxygen:  14.8  p.  ct.;  14.84  p.  ct.  N:  81.8  p.  ct.;  81.73  p.  ct. 

The  residue  after  titration  of  oxygen  and  carbon  dioxide  was  taken 
as  all  nitrogen,  although  it  is  by  no  means  certain  that  some  slight 
fraction  of  carbon  monoxide  may  not  be  included. 

It  is  to  be  noted  that  gases  are  more  easily  drawn  out  of  the  trunk  of 
the  oak  with  its  large  vessels  than  from  either  the  pine  or  walnut. 


SAP  PRESSURES  IN  JUGLANS  MAJOR. 


93 


SAP  PRESSURES  IN  JUGLANS  MAJOR. 

The  walnut  was  selected  for  the  most  comprehensive  test  of  sap 
pressures  in  comparison  with  those  of  the  pine.  Some  measurements 
made  on  the  trunk  of  a  rapidly  growing  tree,  16  years  old,  of  Juglans 
major  were  made  in  September  1924  in  a  preliminary  way.  A  tan¬ 
gential  bore  in  the  trunk  to  which  a  manometer  with  a  closed  end 
had  been  attached  gave  the  following  readings,  in  which  the  length 
of  the  air-column  in  the  manometer  is  expressed  in  mm.  (Table  21). 


Fig.  19. — Trunk  of  Juglans  major  with  four  manometers,  a  dendrograph  and  thermometer 
attached.  A,  radial  bore;  B,  short  stub  of  branch;  C,  tangential  bore;  DD,  branch  4 
meters  in  length.  Manometers  were  also  attached  to  cut  end  of  a  root  and  to  stump  of 
separated  part. 


94 


HYDROSTATIC  SYSTEM  OF  TREES. 


Table  21. 


Date. 

Time. 

Air-column. 

Date. 

Time. 

Air-column. 

mm. 

mm. 

1925 

1925 

Sept.  24 

llh50m 

a.  m. 

67=0 

Sept.  26 

2h 

p.  m. 

65 

12 

m. 

72 

Sept.  27 

4 

p.  m. 

62 

12 

20 

p.  m. 

67 

9 

a.  m. 

62 

3 

45 

p.  m. 

62 

10 

a.  m. 

63 

Sept.  25 

8 

a.  m. 

62 

12 

m. 

63 

11 

30 

a.  m. 

62 

2 

p.  m. 

62 

2 

p.  m. 

61 

Sept.  28 

12 

m. 

63 

4 

p.  m. 

62 

Sept.  29 

8 

a.  m. 

60 

Sept.  26 

8 

a.  m. 

61 

12 

m. 

61 

10 

a.  m. 

65 

Sept.  30 

8 

a.  m. 

60 

12 

m. 

66 

As  soon  as  the  fitting  was  made  some  water  w^as  taken  up  by  the 
elements  contiguous  to  the  cavity,  with  the  result  that  suction  was 
recorded,  the  air-column  being  elongated  from  67  to  72  mm.  Soon 
the  reverse  process  followed,  and  the  air-column  was  compressed,  at 
the  end  showing  a  positive  pressure  of  or  1.1  atmosphere.  Early 
in  the  following  season,  while  the  trunk  was  in  a  condition  of  active 
enlargement,  a  tangential  bore,  8  cm.  in  depth,  was  made  in  the  trunk 
and  fitted  with  a  manometer  with  open  free  arm,  and  a  similar  instru¬ 
ment  was  fitted  by  a  clamped  pressure  hose  to  the  end  of  a  main 
branch  4  meters  in  length,  which  bore  several  leafy  branchlets.  The 
exposed  end  was  16  mm.  in  diameter.  Later  other  attachments  were 
made.  All  readings  are  given  in  terms  of  mm.  Hg.  Suction  being 
indicated  by  —  and  exudation  pressure  by  +  (Table  22). 


Table  22. 


Date. 

Time. 

Tangen¬ 

tial. 

Short 

stub 

Long 

branch. 

Remarks. 

1925 

May  17 

9h05m 

a. 

m. 

65 

Fittings  made. 

9 

35 

a. 

m. 

_ 

8 

_ 

80 

10 

a. 

m. 

14 

_____ 

75 

Air  released  from  both  man- 

3 

30 

P- 

a. 

m. 

3 

10 

ometers;  reset  to  0. 

May  18 
May  19 

May  20 

8 

m. 

3 

___ 

10 

3 

p. 

m. 

_ 

3 

5 

Air  released  and  both  instruments 

8 

a. 

m. 

adjusted  and  reset  to  0. 

3 

30 

p. 

m. 

__ 

0 

_ 

35 

May  21 
May  22 
May  23 
May  24 

2 

P- 

a. 

m. 

10 

_ 

15 

8 

m. 

4 

_ 

20 

8 

30 

a. 

m. 

10 

_ 

10 

9 

a. 

m. 

10 

Air  released  from  tangential  fit¬ 
ting;  reset  to  0. 

10 

a. 

m. 

8 

5 

10 

30 

a. 

m. 

_ 

20 

May  25 

8 

a. 

m. 

+ 

3 

_ 

18 

4 

P- 

a. 

m. 

37 

_ 

30 

May  26 

8 

m. 

+ 

17 

30 

Cloudy. 

Sunny. 

Cloudy. 

11 

30 

a. 

m. 

29 

_ 

26 

May  27 

9 

a. 

m. 

+ 

17 

___ 

37 

3 

P- 

m. 

40 

_ 

35 

SAP  PRESSURES  IN  JUGLANS  MAJOR.  95 


Table  22. — Continued. 


Date. 

Time. 

Tangen¬ 

tial. 

Short 

stub. 

Long 

branch. 

Remarks. 

1925 

May  28 

8h  1)0  a.  m. 

+  48 

-  44 

11  30  a.  m. 

-  25 

-  36 

May  29 

7  30  a.  m. 

+  18 

-  46 

4  p.  m. 

-  30 

-  42 

May  30 

8  a.  m. 

0 

-  47 

11  a.  m. 

-  36 

-  46 

2  p.  m. 

-  37 

-  47 

4  p.  m. 

-  37 

-  49 

May  31 

8  30  a.  m. 

+  17 

-  50 

Raining. 

11  a.  m. 

-  33 

-  40 

5  30  p.  m. 

53 

-  58 

June  1 

7  a.  m. 

+  5 

-  55 

Raining. 

9  a.  m. 

-  5 

-  50 

4  p.  m. 

-100 

-  50 

Clear. 

June  2 

8  a.  m. 

0 

-  58 

Raining. 

12  m. 

-  47 

-  55 

4  p.  m. 

-  70 

-  57 

June  3 

7  a.  m. 

-  5 

-  63 

4  p.  m. 

-110 

-  60 

Clear. 

June  4 

8  a.  m. 

+  12 

-  65 

11  30  a.  m. 

-  30 

-  60 

Clear. 

3  30  p.  m. 

-  37 

-  60 

June  5 

7  a.  m. 

+  28 

-  75 

4  p.  m. 

-  72 

-  65 

Clear. 

June  6 

7  a.  m. 

-  6 

-  78 

Cloudy. 

4  p.  m. 

-  32 

—  65 

June  7 

8  a.  m. 

-  8 

-  70 

Clearing. 

June  8 

7  a.  m. 

-  5 

-  78 

Heavy  fog. 

2  p.  m. 

-  40 

-  67 

Clear. 

June  9 

7  a.  m. 

-  5 

-  78 

10  30  a.  m. 

-  35 

-  70 

June  10 

7i>  a.  m. 

-  7 

-  80 

3  30  p.  m. 

-  26 

-  70 

June  11 

8  a.  m. 

-  10 

-  80 

Cloudy. 

3  p.  m. 

-  26 

-  70 

Clear. 

June  12 

7  a.  m. 

-  8 

-  80 

Air  released  from  tangential  bore; 

reset  to  0. 

3  p.  m. 

-  18 

-  78 

June  13 

7  a.  m. 

-  8 

-  81 

9  a.  m. 

-  9 

-  81 

4  p.  m. 

-  48 

-  78 

June  14 

8  a.  m. 

+  10 

-  81 

Cloudy. 

9  a.  m. 

+  10 

-  81 

Do. 

June  15 

8  a.  m. 

+  33 

-  83 

2  p.  m. 

-  37 

-  67 

Clear. 

June  16 

8  a.  m. 

+  35 

-  83 

Do. 

4  p.  m. 

+  10 

-  80 

Cloudy. 

June  17 

9  a.  m. 

+  55 

-  84 

Do. 

12  m. 

+  40 

-  81 

Do. 

4  p.  m. 

4*  12 

-  79 

Do. 

June  18 

3  p.  m. 

+  18 

-  78 

Do. 

June  19 

7  a.  m. 

+  104 

-  81 

Clear. 

7  30  a.  m. 

-  40 

-  74 

Do. 

8  a.  m. 

+  76 

-  60 

-  72 

Clear;  air  released  from  long 

branch. 

8  30  a.  m. 

+  60 

-  70 

-  2 

9  30  a.  m. 

+  35 

-  76 

-  12 

Clouding. 

11  30  a.  m. 

+  20 

-105 

-  10 

Clearing. 

2  30  p.  m. 

+  5 

-102 

-  25 

Do. 

5  p.  m. 

+  4 

-  98 

-  35 

Fog. 

June  20 

8  a.  m. 

+  134 

-  96 

-  40 

12  m. 

+  95 

-103 

-  40 

Fog. 

June  20 

4  p.  m. 

+  54 

96 

-  40 

Fog. 

June  21 

8  a.  m. 

+  134 

—  45 

Fog;  air  out;  reset  to  0  in  short 

stub. 

12  m. 

+  104 

-  18 

-  48 

Fog. 

96 


HYDROSTATIC  SYSTEM  OF  TREES. 


Table  22. — Continued. 


Date. 

Time. 

Tangen¬ 

tial. 

Short 

stub. 

Long 

branch. 

Remarks. 

1925 
June  22 

yh  m 

a.  m. 

+  152 

-  58 

-  54 

Clearing. 

8  30 

a.  m. 

+  148 

-  50 

-  52 

10 

a.  m. 

+  121 

-  34 

-  52 

Clear. 

4 

p.  m. 

+  10 

-  60 

-  50 

Do. 

June  23 

8 

a.  m. 

+  96 

-  16 

-  43 

Do. 

10  30 

a.  m. 

+  37 

-  25 

-  54 

Do. 

June  24 

7 

a.  m. 

+  66 

-  72 

-  67 

Do. 

11 

a.  m. 

-  1 

-  63 

-  65 

Do. 

2 

p.  m. 

-  26 

-  75 

-  63 

Do. 

June  25 

7 

a.  m. 

+  72 

-  80 

-  62 

Do. 

12 

m. 

-  67 

-  72 

Do. 

4 

p.  m. 

-  42 

-  66 

-  69 

Do. 

June  26 

7 

a.  m. 

+  86 

-  78 

-  81 

Do. 

4  30 

p.  m. 

-  42 

-  69 

-  66 

Do. 

June  27 

8 

a.  m. 

+  78 

-  93 

-  90 

Cloudy. 

3 

p.  m. 

+  54 

-  81 

-  90 

Do. 

June  28 

8 

a.  m. 

+  55 

-  84 

-  90 

Do. 

4 

p.  m. 

-  14 

-  74 

-  96 

June  29 

9 

a.  m. 

+  78 

-  84 

-  97 

Do. 

4 

p.  m. 

+  36 

-  72 

-  96 

Do. 

June  30 

7 

a.  m. 

+  120 

-  70 

-107 

Clear. 

2 

p.  m. 

+  30 

-  96 

Air  released  from  tangential  bore 
and  short  stub.  Reset  to  0; 

dendrograph  fixed  to  trunk. 

July  1 

7 

a.  m. 

+  134 

-  17 

-103 

8 

a.  m. 

+  120 

-  13 

-102 

9 

a.  m. 

+  105 

-  9 

-  99 

Clear. 

Date. 

Time. 

Tangen¬ 

tial. 

Tem¬ 

perature. 

Short 

stub. 

Long 

branch. 

Remarks. 

1925 

°C. 

July  1 

10h  m 

a.  m. 

+  84 
+  72 
+  54 
+  37 
+  37 
+  43 
+  75 
+  158 

-  0 

-104 

Clear. 

11 

a.  m. 

+  3 

+  3 

-  6 

-  99 

Do. 

12 

m. 

-  97 

Do. 

2 

p.  m. 

-  98 

Do. 

3 

p.  m. 
p.  m. 
p.  m. 

-  12 

-  85 

Fog. 

Do. 

4  30 

-  17 

-104 

8 

-  26 

-108 

Do. 

July  2 

7 

a.  m. 

-  26 

-108 

Fog.  Bulb  of  small 
thermometer  inserted 

into  wood  of  1924. 

8 

a.  m. 

+  160 
+  170 
+  176 

-  24 

-110 

Fog. 

Do. 

9  30 

a.  m. 

-  22 

-108 

11 

a.  m. 

14 

-  21 

-110 

7 

p.  m. 

+  88 
+  158 

-  26 

-110 

July  3 

7 

a.  m. 

12.5 

-  28 

-112 

8  30 

a.  m. 

+  168 

13 

-  25 

-112 

11  30 

a.  m. 

+  144 

16 

-  17 

-108 

Clearing. 

2  30 

p.  m. 

+  106 

18 

-  12 

-112 

Do. 

5 

p.  m. 

+  97 

17.5 

-  18 

-110 

Do. 

July  4 

9 

a.  m. 

+  84 

15 

-  18 

-113 

11 

a.  m. 

+  45 

19 

-  4 

-  88 

Sunny. 

3  30 

p.  m. 

-  20 

20 

-  7 

-104 

Do. 

July  5 

8  30 

a.  m. 

+  112 

15 

-  22 

-114 

Overcast. 

10  30 

a.  m. 

+  81 

19 

-  6 

-107 

Clear. 

4  30 

p.  m. 

-  7 

23 

-  5 

-105 

Do. 

July  6 

7 

a.  m. 

+  122 

13 

-  27 

-117 

Do. 

11 

a.  m. 

+  54 

19 

-  9 

-114 

Do. 

6  30 

p.  m. 

+  14 

19 

-  21 

-116 

Do. 

SAP  PRESSURES  IN  JUGLANS  MAJOR. 


97 


Table  22. — Continued. 


Date. 

Time. 

Tangen¬ 

tial. 

Tem¬ 

perature. 

Short 

stub. 

Long 

branch. 

Remarks. 

1925 

°C. 

July  7 

7h  m  a.  m. 

+  126 

13 

-  33 

-122 

Overcast. 

9  a.  m. 

+  126 

14.5 

-  30 

-122 

Do. 

2  p.  m. 

+  111 

20.5 

-  12 

-111 

Clear. 

4  p.  m. 

+  36 

22 

-  12 

-103 

Do. 

July  8 

7  30  a.  m. 

+  126 

14 

-  34 

-117 

Overcast. 

9  30  a.  m. 

+  111 

16.5 

-  22 

-122 

Clearing. 

2  p.  m. 

+  24 

20 

-  14 

-117 

Clear. 

4  p.  m. 

+  14 

18.5 

-  21 

-122 

Overcast. 

July  9 

7  30  a.  m. 

+  94 

14.5 

-  36 

-118 

Drizzle  and  fog. 

10  30  a.  m. 

+  98 

16 

-  29 

-126 

Do. 

4  p.  m. 

+  38 

19 

-  16 

-177 

Overcast. 

July  11 

7  30  a.  m. 

+  107 

15 

-  33 

-128 

Clear. 

11  a.  m. 

-  2 

23 

-  0 

-116 

Do. 

2  30  p.  m. 

-  66 

23.5 

-  0 

-108 

Do. 

3  15  p.  m. 

-  66 

23.5 

-  3 

-100 

Do. 

4  30  p.  m. 

-  60 

27 

-  9 

-  98 

Do. 

July  12 

8  a.  m. 

+  122 

17 

-  12 

-122 

Do. 

10  30  a.  m. 

+  7 

24 

+  7 

-113 

Do. 

July  13 

7  30  a.  m. 

+  60 

14 

-  32 

-138 

Do. 

9  30  a.  m. 

+  30 

20 

-  8 

-116 

Do. 

12  m. 

-  12 

22.5 

+  5 

-114 

Do. 

3  30  p.  m. 

-  50 

26 

-  3 

-112 

Do. 

July  14 

7  30  a.  m. 

+  60 

15 

-  36 

-132 

Do. 

11  15  a.  m. 

+  17 

19.5 

-  18 

-126 

Clouds. 

2  15  p.  m. 

-  21 

23 

-  14 

-117 

July  15 

7  30  a.  m. 

+  25 

13 

-  51 

-138 

Fog. 

9  30  a.  m. 

+  18 

16 

-  35 

-130 

Clear. 

1  30  p.  m. 

-  24 

19 

-  36 

-137 

Do. 

July  16 

7  a.  m. 

+  12 

14.5 

-  48 

-138 

Do. 

11  a.  m. 

-  28 

19 

-  36 

-130 

Do. 

3  p.  m. 

-  48 

22.5 

-  36 

-127 

Clear. 

July  17 

7  a.  m. 

+  15 

15 

-  35 

-126 

Do. 

3  15  p.  m. 

-  52 

23 

-  36 

-124 

Do. 

July  18 

7  a.  m. 

+  12 

15 

-  48 

-142 

Clouds. 

11  30  a.  m. 

-  24 

19.5 

-  24 

-129 

Do. 

4  p.  m. 

-  30 

19 

-  36 

-130 

Do. 

July  19 

7  40  a.  m. 

-  8 

17 

-  42 

-140 

Do. 

10  a.  m. 

-  24 

18 

-  37 

-138 

Do. 

5  p.  m. 

-  8 

17 

-  47 

-141 

Do. 

July  20 

7  a.  m. 

-  2 

14.5 

-  60 

-147 

Cloudy. 

11  30  a.  m. 

-  15 

18 

-  39 

-139 

Do. 

3  30  p.  m. 

-  44 

24.5 

-  28 

-135 

Clear. 

July  21 

7  a.  m. 

-  0 

15 

-  54 

-146 

Overcast. 

11  a.  m. 

-  18 

18 

-  42 

-118 

Do. 

4  p.  m. 

-  31 

18 

-  42 

-144 

Clouds. 

July  22 

7  a.  m. 

-  1 

14 

-  66 

-151 

Drizzle. 

11  a.  m. 

•  •••••••• 

15 

-  67 

-151 

4  30  p.  m. 

-  20 

18 

-  53 

-146 

Overcast. 

July  23 

8  a.  m. 

-  0 

14.5 

-  68 

-153 

Do. 

11  45  a.  m. 

-  41 

19 

-  42 

-137 

Clear. 

4  p.  m. 

-  28 

22 

-  45 

-137 

Do. 

July  24 

7  30  a.  m. 

-  6 

13 

-  71 

-160 

Cloudy. 

4  p.  m. 

-  31 

21 

-  50 

-147 

Clouds. 

8  p.  m. 

-  10 

15 

-  66 

-153 

July  25 

7  30  a.  m. 

+  2 

13 

-  74 

-158 

Overcast. 

9  a.  m. 

-  0 

15 

-  60 

-153 

Clear. 

12  m. 

-  25 

19 

-  48 

-142 

Do. 

3  p.  m. 

-  24 

19 

-  55 

-150 

Clouds. 

July  26 

7  30  a.  m. 

+  9 

13 

-  78 

-162 

Air  released  from  in- 

strument  at  end  of 

long  branch ;  reset  at  0. 

98 


HYDROSTATIC  SYSTEM  OF  TREES. 


Table  22. — Continued. 


Date. 

Time. 

T  angen 
tial. 

Tem¬ 

perature. 

Short 

branch. 

Long 

branch. 

Remarks. 

1925 

°C. 

July 

6 

10h 

m 

a. 

m. 

15 

69 

-  10 

3 

P- 

m. 

-  17 

18 

60 

-138 

Again  reset  at  —132. 

Overcast. 

July 

27 

7 

30 

a. 

m. 

+  5 

13 

75 

-134 

Overcast. 

11 

30 

a. 

m. 

-  5 

15 

67 

-134 

Do. 

2 

30 

P- 

m. 

-  12 

17 

63 

-133 

Do. 

July 

28 

7 

a. 

m. 

+  3 

13 

79 

-138 

Do. 

11 

a. 

m. 

-  7 

16 

66 

-134 

Do. 

2 

P- 

in. 

-  14 

19 

54 

-134 

Clear. 

July 

29 

7 

40 

a. 

m. 

+  2 

13 

75 

-139 

Overcast. 

July 

30 

8 

a. 

m. 

+  3 

13 

75 

-138 

Dripping  fog. 

4 

P- 

m. 

-  14 

17 

64 

-134 

Overcast. 

July 

31 

7 

30 

a. 

m. 

-  4 

13 

76 

-141 

Do. 

11 

30 

a. 

m. 

-  12 

17 

62 

-137 

Clearing. 

Aug. 

2 

3 

45 

P- 

m. 

-  14 

18 

63 

-137 

Do. 

Aug. 

3 

7 

30 

a. 

m. 

-  3 

12 

83 

-147 

Overcast. 

11 

30 

a. 

m. 

-  18 

18 

60 

-133 

Clear. 

3 

40 

P- 

m. 

-  18 

22 

54 

-137 

Do. 

Aug. 

4 

8 

a. 

m. 

-  0 

12 

80 

-147 

Overcast. 

2 

30 

P- 

m. 

-  13 

18 

60 

-141 

Clear.  Air  released 

from  short  branch; 

- 

reset  at  60. 

Aug. 

5 

9 

a. 

m. 

-  2 

13 

48 

-150 

Overcast. 

Aug. 

6 

2 

30 

P- 

m. 

-  18 

23 

15 

-132 

Clear. 

Aug. 

7 

9 

a. 

m. 

-  9 

39 

-147 

Do. 

4 

P- 

m. 

-  28 

22 

19 

-139 

Do. 

Aug. 

8 

8 

a. 

m. 

-  3 

14 

.  5 

42 

-147 

Fog. 

Tan- 

Tern- 

Short 

Long 

Date. 

Time. 

gential. 

Radial. 

perature. 

stub. 

branch. 

Remarks. 

1925 

°C. 

Aug. 

8 

9h30m 

a. 

m. 

-  5 

18 

-42 

-150 

Overcast.  A  radial  bore  was 

now  made  7  cm.  in  depth 

above  and  parallel  to  tan- 

gential  bore  and  30  cm.  from 

base  of  short  stub  of  branch, 

and  30°  from  it.  Readings 

are  given  in  separate  col- 

umns. 

10 

30 

a. 

m. 

-  8 

-38 

-148 

Overcast. 

7 

P- 

m. 

-26 

-  3 

-33 

-135 

Clearing.  Air  released  from  in- 

strument  on  radial  bore; 

reset  to  0. 

Aug. 

10 

8 

a. 

m. 

-  7 

-  0 

15 

-39 

-146 

Clear. 

11 

a. 

m. 

-15 

-55 

-48 

-152 

Overcast. 

4 

P- 

m. 

-27 

-64 

-26 

-148 

Clear.  Air  released  from  in- 

strument  on  short  stub;  re- 

set  to  0. 

Aug. 

11 

8 

a. 

m. 

-  4 

-45 

15 

-12 

-146 

Clear. 

11 

30 

a. 

m. 

-24 

-48 

20 

-12 

-137 

Do. 

7 

P- 

m. 

-24 

-16 

-32 

-151 

Do. 

Aug. 

12 

7 

30 

a. 

m. 

-  0 

-48 

15 

-30 

-151 

Do. 

11 

30 

a. 

m. 

-19 

-47 

21 

-16 

-137 

Do. 

4 

15 

P- 

m. 

-30 

-54 

-24 

-149 

Do. 

Aug. 

13 

7 

30 

a. 

m. 

0 

-51 

13 

-51 

-160 

Overcast. 

11 

30 

a. 

m. 

-  7 

-48 

18 

-33 

-158 

Do. 

7 

P- 

m. 

-28 

-54 

18 

-48 

-156 

Clear  afternoon. 

Aug. 

14 

5 

45 

a. 

m. 

+  8 

-51 

12 

-63 

-164 

Overcast. 

8 

45 

a. 

m. 

+  5 

-47 

15 

-47 

-158 

Clearing. 

Aug. 

15 

11 

a. 

m. 

-  7 

-45 

17 

-48 

-159 

Overcast. 

SAP  pressures  in  juglans  major 


99 


Table  22. — Continued. 


Date. 

Time. 

Tan¬ 

gential. 

Radial. 

Tem¬ 

perature. 

Short 

stub. 

Long 

branch. 

Remarks. 

1925 

C. 

Aug.  16 

7h30m 

a.  m. 

0 

-57 

15 

-57 

-162 

Overcast. 

4 

p.  m. 

-  9 

-48 

18 

-51 

-160 

Do. 

Aug.  17 

7  30 

a.  m. 

+  6 

-51 

15 

-66 

-165 

Clear  at  9h30m  a.  m. 

11  30 

a.  m. 

-12 

-56 

20 

-56 

-144 

4 

p.  m. 

-21 

-59 

19 

-51 

-158 

Clear. 

Aug.  18 

7  30 

a.  m. 

4-12 

-45 

13 

-56 

-162 

Do. 

11 

a.  m. 

-12 

-41 

20 

-43 

-150 

Do. 

4 

p.  m. 

-21 

-51 

20 

-56 

-162 

Aug.  19 

7 

a.  m. 

4-14 

-48 

12 

-75 

-170 

Do. 

11  45 

a.  m. 

-15 

-40 

20 

-44 

-152 

Do. 

4  15 

p.  m. 

-27 

-54 

18 

-60 

-165 

Do. 

Aug.  20 

7  30 

a.  m. 

+  2 

-51 

14 

-75 

-174 

Overcast. 

11  30 

a.  m. 

-10 

-45 

18 

-56 

-147 

Clear. 

Aug.  21 

3  30 

p.  m. 

-32 

-54 

22 

-50 

-162 

Do. 

Aug.  22 

8 

a.  m. 

+  2 

-49 

18 

-43 

-165 

Do. 

11  30 

a.  m. 

-18 

-48 

22 

-55 

-153 

Do. 

5 

p.  m. 

-42 

-65 

20 

-60 

-160 

Clear.1 

Date. 

Time. 

Tan¬ 

gential. 

Radial. 

Tem¬ 

pera¬ 

ture. 

Short 

stub. 

Long 

branch. 

Rc 

Ter¬ 

minal. 

>ot. 

Stump. 

Remarks. 

1925 

°C. 

Aug.  23 

llh15m 

a.  m. 

— 

13 

— 

19 

0 

— 

10 

— 

4 

+  U8 

Air  was  released  from 

4 

30 

p.  m. 

— 

24 

— 

43 

— 

6 

— 

18 

— 

28 

+  138 

all  manometers  ex- 

cept  that  on  de- 

// 

tached  root  at  8 

a.  m.  on  23d  and 

reset  to  0. 

Aug.  24 

7 

30 

a.  m. 

— 

10 

— 

48 

16 

— 

1 

— 

21 

+ 

14 

+  156 

Pressure  in  stump  of 

11 

30 

a.  m. 

— 

24 

— 

60 

+ 

14 

— 

12 

— 

21 

+  91 

root  was  +118, 

which  was  not  dis- 

turbed. 

4 

p.  m. 

— 

23 

— 

74 

— 

27 

— 

27 

— 

38 

+  87 

Clear. 

Aug.  25 

7 

30 

a.  m. 

+ 

2 

— 

62 

— 

24 

— 

33 

+ 

16 

+  108 

Do. 

11 

30 

a.  m. 

— 

12 

— 

58 

14 

— 

5 

— 

21 

— 

17 

+  96 

Do. 

Aug.  26 

8 

a.  m. 

— 

9 

— 

72 

— 

19 

— 

35 

— 

27 

+  84 

Do. 

11 

30 

a.  m. 

— 

13 

— 

63 

— 

40 

— 

45 

— 

12 

+84 

Overcast. 

7 

15 

p.  m. 

_ 

11 

_ 

62 

_ 

53 

__ 

54 

Aug.  27 

6 

a.  m. 

— 

8 

— 

68 

12 

— 

51 

— 

55 

— 

21 

+  71 

Do. 

7 

a.  m. 

— 

— 

67 

12 

— 

36 

— 

53 

— 

21 

+  70 

Clear. 

8 

a.  m. 

— 

7 

— 

62 

16 

— 

32 

— 

48 

— 

9 

+  75 

Clouds. 

9 

a.  m. 

— 

21 

— 

60 

18 

— 

24 

— 

47 

+ 

5 

+  78 

Do. 

10 

a.  m. 

— 

21 

— 

63 

19 

— 

24 

— 

41 

+ 

5 

+  78 

11 

a.  m. 

— 

23 

— 

63 

— 

26 

— 

43 

+ 

6 

+  73 

Do. 

12 

m. 

— 

30 

— 

66 

20 

— 

32 

— 

47 

+ 

3 

+  71 

2 

p.  m. 

— 

38 

— 

71 

18 

— 

33 

— 

48 

— 

3 

+  66 

Overcast. 

3 

p.  m. 

— 

41 

— 

73 

17 

— 

36 

— 

50 

— 

6 

+  62 

Do. 

4 

p.  m. 

— 

39 

— 

74 

15 

— 

50 

— 

51 

— 

9 

+  57 

Do. 

5 

p.  m. 

— 

38 

— 

76 

13 

— 

50 

— 

55 

— 

15 

+  56 

Do. 

8 

p.  m. 

— 

30 

— 

78 

10 

— 

61 

— 

60 

— 

24 

+  44 

Do. 

11 

p.  m. 

— 

20 

— 

81 

10 

— 

66 

— 

60 

— 

32 

+  36 

Overcast. 

Aug.  28 

3 

a.  m. 

— 

15 

— 

79 

10 

— 

65 

— 

62 

— 

29 

+  35 

Do. 

4 

a.  m. 

— 

15 

— 

80 

10 

— 

65 

— 

62 

— 

18 

+  36 

Do. 

6 

a.  m. 

— 

17 

— 

78 

10 

— 

59 

— 

60 

— 

15 

+  36 

Do. 

1  Root  lying  30  cm.  deep  was  cut  1.6  meters  from  base  of  trunk  when  it  showed  a  diameter  of  24  to  26 
mm.  and  a  section  30  cm.  long  removed.  Manometers  with  open  ends  were  attached  by  wired  sections 
of  pressure  hose  to  terminal  of  part  attached  to  tree  and  to  stump  of  detached  part.  Apparatus  was 
completely  fixed  Aug.  22,  4.30  p.  m.  Suction  of  —12  mm.  was  shown  by  terminal  of  root  within  a  half 
hour,  and  —40  mm.  Hg.  by  stump  of  detached  part. 


100 


HYDROSTATIC  SYSTEM  OF  TREES 


Table  22. — Continued. 


Date. 

Time. 

Tan¬ 

gential. 

Radial. 

Tem¬ 

pera¬ 

ture. 

Short 

stub. 

Long 

branch. 

Root. 

Remarks. 

Ter¬ 

minal. 

Stump. 

1925 

°C. 

Aug.  28 

8h  ™ 

a.  m. 

— 

17 

— 

74 

10 

-  50 

-  57 

— 

8 

+  38 

Overcast. 

9 

a.  m. 

— 

21 

— 

71 

12 

-  37 

-  52 

+ 

3 

+  43 

Clear. 

10 

a.  m. 

— 

19 

— 

68 

13 

-  41 

-  53 

+ 

9 

+  44 

Do. 

11 

a.  m. 

— 

21 

— 

69 

15 

-  37 

-  51 

+ 

8 

+  43 

Do. 

2 

p.  m. 

— 

30 

— 

72 

16 

-  43 

-  55 

+ 

2 

+  36 

Do. 

4 

p.  m. 

— 

33 

— 

75 

18 

-  54 

-  60 

— 

1 

+  31 

Clear  at  sunset. 

7 

p.  m. 

— 

29 

— 

80 

15 

-  62 

-  62 

— 

19 

+  15 

Overcast. 

9 

p.  m. 

— 

18 

— 

81 

12 

-  66 

-  66 

— 

25 

+  9 

Do. 

Aug.  29 

3 

a.  m. 

— 

15 

— 

77 

12 

-  64 

-  65 

— 

15 

+  3 

Do. 

4 

a.  m. 

— 

22 

— 

77 

12 

-  63 

-  66 

— 

15 

+  3 

Do. 

6 

a.  m. 

— 

17 

— 

75 

13 

-  65 

-  66 

— 

13 

-  0 

Do. 

Aug.  30 

9 

a.  m. 

— 

19 

— 

66 

15 

-  67 

-  72 

— 

10 

-  21 

Fog  and  heavy  dew. 

12 

m. 

— 

63 

— 

64 

18 

-  48 

-  63 

+ 

3 

-  18 

Clear. 

6 

p.  m. 

— 

31 

— 

78 

17 

-  62 

-  72 

— 

18 

-  22 

Do. 

Aug.  31 

9 

a.  m. 

— 

19 

— 

68 

15 

-  63 

-  72 

+ 

7 

-  32 

Overcast. 

4 

p.  m. 

— 

38 

— 

78 

20 

-  54 

-  71 

— 

3 

-  36 

Clouds. 

Sept.  1 

7 

a.  m. 

— 

18 

— 

75 

13 

-  75 

-  83 

— 

3 

-  48 

12 

m. 

— 

22 

— 

68 

21 

-  45 

-  66 

+ 

8 

-  43 

Clear. 

7 

p.  m. 

— 

35 

— 

92 

15 

-  74 

-  84 

— 

18 

-  60 

Do. 

Sept.  2 

7 

a.  m. 

— 

15 

— 

72 

12 

-  81 

-  72 

+ 

12 

-  63 

Clear.  Air  released 

from  radial  bore; 

column  reset  at 

-72. 

11 

a.  m. 

— 

22 

— 

75 

20 

-  54 

-  72 

+ 

17 

-  54 

Clear. 

Sept.  5 

11 

a.  m. 

— 

26 

— 

80 

-  55 

-  71 

— 

0 

-  90 

Do. 

6  30 

p.  m. 

— 

31 

— 

87 

-  72 

-  98 

— 

2 

-108 

Clouds. 

Sept.  6 

8  30 

a.  m. 

— 

14 

— 

94 

-  75 

-102 

+ 

2 

-129 

Clearing. 

6 

p.  m. 

— 

30 

— 

78 

20 

-  63 

-  98 

— 

3 

-106 

Clear. 

Sept.  7 

7  30 

a.  m. 

— 

12 

— 

74 

-  80 

-105 

— 

0 

-110 

Clear. 

11  15 

a.  m. 

— 

33 

— 

72 

21 

-  62 

-  92 

— 

0 

-104 

4  30 

p.  m. 

— 

32 

— 

31 

20 

-  73 

-103 

— 

3 

-114 

Sept.  8 

7  30 

a.  m. 

— 

5 

— 

75 

14 

-  87 

-111 

+ 

3 

-122 

11  30 

a.  m. 

— 

33 

— 

72 

-  63 

-  94 

— 

3 

-108 

Clear.  Air  released 

from  short  stub; 

reset  at  — 63. 

4 

p.  m. 

— 

25 

— 

81 

20 

-  80 

-108 

— 

3 

-114 

Clear. 

Sept.  9 

8 

a.  m. 

— 

10 

— 

78 

-  98 

-118 

— 

6 

-127 

Do. 

11  30 

a.  m. 

— 

24 

— 

48 

22 

-  75 

-104 

— 

5 

-115 

Cloudy. 

Sept.  10 

7  30 

a.  m. 

— 

6 

— 

30 

15 

-  96 

-123 

— 

3 

-132 

Clearing. 

Sept.  13 

8 

a.  rn. 

— 

6 

— 

32 

10 

-  98 

-134 

— 

3 

-138 

Clear. 

6 

p.  m. 

— 

32 

— 

50 

17 

-102 

-137 

— 

5 

-144 

Do. 

Sept.  14 

7  15 

a.  m. 

— 

2 

— 

42 

11 

-114 

-144 

— 

1 

-152 

Do. 

11  30 

a.  m. 

— 

36 

— 

48 

20 

-  90 

-124 

— 

3 

-132 

Do. 

4 

p.  m. 

— 

33 

— 

54 

20 

-  97 

-135 

— 

5 

-141 

Do. 

Sept.  15 

7  15 

a.  m. 

+ 

3 

— 

56 

12 

-110 

-141 

+ 

3 

-156 

Clear. 

3  30 

p.  m. 

— 

33 

— 

60 

22 

-  88 

-134 

— 

5 

-134 

Do. 

Sept.  16 

7  30 

a.  m. 

+ 

9 

— 

57 

14 

-106 

-144 

+ 

1 

-152 

Do. 

Sept.  18 

7 

a.  m. 

— 

3 

— 

74 

11 

-135 

-151 

+ 

0 

-150 

Do. 

Sept.  20 

9 

a.  m. 

+ 

3 

— 

66 

15 

-104 

-153 

+ 

5 

-145 

Do. 

Sept.  21 

7  30 

a.  m. 

— 

10 

— 

75 

13 

-114 

-162 

+ 

3 

-156 

Do. 

11  30 

a.  m. 

20 

_ 

61 

25 

-  88 

-136 

Do. 

4 

p.  m. 

— 

42 

— 

72 

20 

-108 

-161 

— 

22 

-150 

Do. 

Sept.  22 

7  30 

a.  m. 

— 

7 

— 

68 

15 

-111 

-156 

+ 

3 

-156 

Do. 

11  30 

a.  m. 

— 

19 

— 

63 

24 

-  96 

-152 

— 

10 

-132 

Do. 

5  30 

p.  m. 

— 

12 

— 

70 

18 

-115 

-169 

— 

12 

-151 

Cloudy. 

Sept.  23 

8 

a.  m. 

+ 

4 

— 

72 

12 

-132 

-178 

— 

4 

-160 

Do. 

12 

m. 

+ 

12 

— 

60 

-108 

-154 

— 

4 

-142 

Do. 

4 

p.  m. 

— 

3 

— 

59 

19 

-X16 

-171 

— 

9 

-150 

Do. 

SAP  PRESSURES  IN  JUGLANS  MAJOR 


101 


Table  22. — Continued. 


Date. 

Time. 

Tan¬ 

gential. 

Radial. 

Tem¬ 

pera¬ 

ture. 

Short 

stub. 

Long 

branch. 

Rc 

Ter¬ 

minal. 

>ot. 

Stump. 

Remarks. 

1925 

°C. 

Sept.  24 

7h15m 

a.  m. 

+ 

18 

— 

66 

12 

-134 

-182 

— 

6 

-165 

Clearing. 

11 

30 

a.  m. 

— 

16 

— 

54 

17 

-116 

-176 

+ 

2 

-144 

Clouds. 

4 

p.  m. 

— 

1 

— 

56 

19 

-117 

-177 

— 

15 

-150 

Clear. 

Sept.  25 

8 

a.  m. 

+ 

10 

— 

48 

13 

-120 

-180 

+ 

5 

-158 

Do. 

5 

p.  m. 

— 

30 

— 

54 

18 

-118 

-181 

— 

14 

-150 

Do. 

Sept.  26 

7 

15 

a.  m. 

— 

4 

— 

65 

12 

-132 

-182 

— 

1 

-162 

Do. 

11 

45 

a.  m. 

— 

12 

— 

41 

23 

-103 

-168 

— 

3 

-128 

Do. 

4 

p.  m. 

— 

32 

— 

42 

21 

-114 

-181 

13 

-148 

Do. 

Sept.  28 

7 

30 

a.  m. 

+ 

0 

— 

56 

15 

-128 

-192 

_ 

3 

-168 

Air  released  from  radial 

bore;  reset  to  — 56. 

Sept.  29 

9 

45 

a.  m. 

— 

10 

— 

60 

13 

-130 

-195 

+ 

10 

-162 

Clear. 

Sept.  30 

4 

p.  m. 

— 

22 

— 

57 

23 

-116 

-192 

— 

15 

-144 

Clear.  Air  released 

from  4  instruments 

on  trunk  and 

branches;  reset 

at  0. 

Oct.  4 

9 

a.  m. 

.  , 

•  •  •  • 

— 

30 

21 

-  48 

-  58 

+ 

27 

-156 

Clear.  Stopcock  left 

open  on  tangential 

bore. 

4 

p.  m. 

•  •  • 

— 

22 

-  57 

-  64 

— 

18 

—  165 

Clear. 

Oct.  5 

7 

30 

a.  m. 

.  . 

•  •  • 

— 

37 

10 

-  70 

-  74 

— 

4 

-183 

Do. 

2 

30 

p.  m. 

#  , 

•  •  • 

— 

24 

-  45 

-  70 

+ 

3 

-150 

Clouds. 

Oct.  6 

7 

30 

a.  m. 

•  •  • 

— 

38 

11 

-  75 

-  80 

— 

6 

-186 

Clear. 

5 

p.  m. 

•  •  • 

— 

30 

19 

-  70 

-  79 

— 

18 

-168 

Do. 

Oct.  7 

7 

45 

a.  m. 

+ 

14 

— 

42 

12 

-  78 

-  86 

— 

2 

-188 

Clear.  Stopcock 

closed  on  tangen- 

tial  bore. 

• 

12 

m. 

— 

6 

— 

26 

25 

-  51 

-  78 

+ 

17 

-158 

Clear. 

3 

15 

p.  m. 

— 

27 

— 

30 

23 

-  67 

-  84 

— 

14 

-168 

Do. 

6 

30 

p.  m. 

— 

27 

— 

38 

17 

-  84 

-  90 

— 

42 

-186 

Do. 

Oct.  8 

7 

30 

a.  m. 

— 

5 

— 

44 

10 

-  94 

-  96 

— 

8 

-192 

Do. 

4 

p.  m. 

— 

26 

— 

38 

22 

-  77 

-  91 

— 

15 

-176 

Do. 

Oct.  9 

7 

30 

a.  m. 

— 

3 

— 

49 

12 

-  93 

-102 

— 

3 

-192 

Clouds. 

3 

30 

p.  m. 

— 

0 

— 

42 

17 

-  84 

-  99 

— 

3 

-172 

Do. 

Oct.  10 

8 

a.  m. 

— 

5 

— 

39 

15 

-  96 

-106 

— 

5 

-182 

Overcast. 

12 

m. 

— 

0 

— 

41 

17 

-  89 

-104 

+ 

4 

-172 

Do. 

4 

p.  m. 

— 

2 

— 

42 

17 

-  92 

-106 

— 

9 

-178 

Do. 

Oct.  1 1 

8 

a.  m. 

+ 

4 

— 

44 

15 

-104 

-111 

— 

7 

-182 

Do. 

Oct.  12 

8 

a.  m. 

+ 

6 

— 

48 

9 

-112 

-121 

— 

18 

-196 

Cloudy,  raining  since 

noon  of  11th. 

4 

p.  m. 

— 

13 

— 

38 

18 

-  96 

-116 

+ 

2 

-178 

Cloudy.  Clear  in 

afternoon. 

Oct.  13 

8 

a.  m. 

+ 

12 

— 

51 

9 

-111 

-125 

— 

20 

-196 

Clear. 

2 

p.  m. 

— 

12 

— 

34 

22 

-  91 

-120 

+ 

5 

-160 

Do. 

Oct.  14 

8 

a.  m. 

— 

8 

— 

50 

10 

-114 

-128 

— 

18 

-191 

Do. 

Oct.  16 

9 

a.  m. 

+ 

7 

— 

42 

13 

-119 

-134 

— 

20 

-182 

Cloudy. 

4 

p.  m. 

— 

3 

— 

38 

16 

-115 

-134 

— 

19 

-172 

Do. 

Oct.  17 

9 

a.  m. 

+ 

4 

— 

39 

13 

-122 

-140 

— 

30 

-195 

Do. 

Oct.  18 

8 

a.  m. 

+ 

4 

— 

48 

11 

-123 

-146 

— 

19 

-188 

Clear. 

Oct.  19 

9 

a.  m. 

— 

2 

— 

45 

13 

-122 

-148 

— 

26 

-194 

Do. 

4 

p.  m. 

— 

30 

— 

22 

23 

-106 

-142 

— 

6 

-172 

Do. 

Oct.  20 

7 

30 

a.  m. 

— 

13 

— 

45 

14 

-120 

-150 

— 

27 

-190 

Do. 

2 

p.  m. 

— 

28 

— 

22 

25 

-105 

-144 

— 

2 

-162 

Do. 

Oct.  21 

8 

a.  m. 

— 

12 

— 

51 

15 

-122 

-156 

— 

27 

-187 

Do. 

Oct.  22 

4 

p.  m. 

— 

3 

— 

46 

19 

-122 

-158 

— 

24 

-175 

Do. 

Oct.  23 

7 

a.  m. 

+ 

2 

— 

60 

13 

-136 

-164 

— 

45 

-186 

Do. 

11 

a.  m. 

— 

3 

— 

42 

21 

-110 

-153 

— 

9 

-162 

Do. 

Oct.  24 

7 

a.  m. 

+ 

5 

— 

67 

14 

-144 

-170 

— 

54 

-198 

Do. 

12 

m. 

— 

4 

— 

37 

24 

-  81 

-158 

— 

4 

-158 

Do. 

7 

p.  m. 

— 

18 

— 

48 

15 

-135 

-167 

— 

42 

-180 

Do. 

102 


HYDROSTATIC  SYSTEM  OF  TREES. 


Table  22. — Continued. 


Date. 

Time. 

Tan¬ 

gential. 

Radial. 

Tem¬ 

pera¬ 

ture. 

Short 

stub. 

Long 

branch. 

Root. 

Remarks. 

Ter¬ 

minal. 

Stump. 

1925 

°C. 

Oct.  25 

8h  m 

a.  m. 

— 

5 

— 

60 

14 

-134 

-170 

— 

30 

-182 

Clear. 

Oct.  26 

7  30 

a.  m. 

— 

16 

— 

60 

15 

-136 

-177 

— 

39 

-187 

Do. 

Oct.  27 

8 

a.  m. 

+ 

5 

— 

66 

12 

-146 

-186 

— 

42 

-186 

Do. 

4 

p.  m. 

— 

3 

— 

51 

17 

-124 

-139 

— 

30 

-180 

Do. 

Oct.  28 

7  30 

a.  m. 

+ 

3 

— 

66 

11 

-150 

-192 

— 

41 

-190 

Overcast. 

4 

p.  m. 

— 

1 

— 

50 

15 

-138 

-186 

— 

20 

-170 

Do. 

Oct.  29 

2 

p.  m. 

— 

3 

— 

36 

20 

-129 

-180 

— 

19 

-162 

Clear. 

Oct.  30 

7  30 

a.  in. 

+ 

4 

— 

57 

11 

-150 

-188 

— 

44 

-198 

Overcast. 

Oct.  31 

8 

a.  m. 

+ 

2 

— 

45 

14 

-144 

-199 

— 

36 

-170 

Do. 

Nov.  1 

10  30 

a.  m. 

+ 

5 

— 

42 

15 

-140 

-204 

— 

32 

-140 

Do. 

Nov.  2 

8 

a.  m. 

+ 

4 

— 

44 

12 

-149 

-204 

— 

37 

-171 

Showers. 

Nov.  3 

9 

a.  m. 

+ 

4 

— 

53 

9 

-152 

-205 

— 

37 

-168 

Clearing. 

Nov.  4 

8 

a.  m. 

— 

0 

— 

43 

9 

-153 

-207 

— 

45 

-174 

Clear. 

4 

p.  m. 

— 

3 

— 

38 

-142 

-204 

— 

36 

-156 

Do. 

Nov.  5 

8 

a.  m. 

— 

0 

— 

63 

60 

-160 

-228 

— 

54 

-178 

Do. 

4 

p.  m. 

— 

7 

— 

41 

14 

-148 

-204 

— 

42 

-168 

Do. 

Nov.  6 

8 

a.  m. 

— 

6 

— 

66 

4 

-165 

-232 

— 

48 

-178 

Do. 

3 

p.  m. 

— 

4 

— 

40 

15 

-139 

-204 

— 

20 

-144 

Do. 

Nov.  7 

8 

a.  m. 

+ 

2 

— 

60 

5 

-158 

-222 

— 

41 

-168 

Do. 

Nov.  8 

10 

a.  m. 

+ 

12 

— 

37 

14 

-135 

-218 

— 

18 

-138 

Do. 

Nov.  9 

8 

a.  m. 

— 

2 

— 

50 

5 

-150 

-231 

— 

56 

-163 

Do. 

3 

p.  m. 

— 

4 

— 

24 

15 

-132 

-222 

— 

8 

-138 

Cloudy. 

Nov.  10 

4 

p.  m. 

— 

3 

— 

9 

16 

-134 

-218 

— 

15 

-126 

Do. 

Nov.  11 

7  30 

a.  m. 

+ 

4 

— 

19 

14 

-139 

-234 

— 

21 

-126 

Raining. 

4 

p.  m. 

— 

0 

— 

10 

15 

-138 

-234 

— 

18 

-126 

Do. 

Nov.  12 

8 

a.  m. 

+ 

4 

— 

20 

15 

-151 

-240 

— 

31 

-138 

Cloudy. 

4 

p.  m. 

— 

5 

— 

3 

16 

-136 

-260 

— 

18 

-126 

Raining. 

Nov.  13 

7  30 

a.  m. 

— 

3 

— 

24 

6 

-160 

-268 

— 

50 

-156 

Clear. 

Nov.  14 

7  30 

a.  m. 

— 

5 

— 

32 

4 

-162 

-256 

— 

54 

-156 

Do. 

4 

p.  m. 

— 

4 

— 

8 

14 

-140 

-248 

— 

30 

-138 

Do. 

Nov.  15 

8 

a.  m. 

— 

3 

— 

27 

7 

-136 

-256 

— 

42 

-144 

Do. 

1  30 

p.  m. 

— 

2 

— 

0 

18 

-126 

-246 

— 

7 

-144 

Do. 

6 

p.  m. 

— 

9 

— 

10 

12 

-148 

-257 

— 

7 

-143 

Cloudy. 

Nov.  16 

8 

a.  m. 

+ 

3 

— 

8 

12 

-142 

-256 

— 

19 

-132 

Drizzle. 

Nov.  17 

7  30 

a.  m. 

— 

3 

— 

18 

7 

-156 

-260 

— 

48 

-144 

Clear. 

Nov.  18 

7  30 

a.  m. 

— 

4 

— 

9 

7 

-155 

-265 

— 

48 

-144 

Do. 

11  30 

a.  m. 

+ 

3 

+ 

14 

19 

-129 

-252 

— 

4 

-114 

Do. 

2 

p.  m. 

— 

8 

+ 

15 

22 

-121 

-248 

— 

15 

-120 

Do. 

7 

p.  m. 

— 

14 

— 

2 

10 

-150 

-264 

— 

48 

-162 

Do. 

Nov.  19 

7  30 

a.  m. 

— 

10 

— 

12 

8 

-154 

-263 

— 

48 

-138 

Do. 

Nov.  20 

8 

a.  m. 

— 

9 

— 

7 

8 

-150 

-266 

— 

39 

-138 

Clear.  Air  released 

from  short  stub  of 

branch. 

11  30 

a.  m. 

+ 

9 

+ 

26 

22 

+  21 

-258 

+ 

3 

Clear.  Stump  of  root 

taken  up. 

2 

p.  m. 

— 

5 

+ 

30 

22 

+  4 

-250 

— 

8 

Clear. 

4  30 

p.  m. 

— 

14 

+ 

18 

16 

-  12 

-258 

— 

30 

Do. 

Nov.  21 

8 

a.  m. 

— 

12 

— 

2 

10 

-  29 

-260 

— 

38 

Overcast. 

12 

m. 

+ 

5 

+ 

24 

18 

-  16 

-256 

+ 

3 

Slightly  overcast. 

4 

p.  m. 

— 

3 

+ 

24 

18 

-  15 

-258 

— 

8 

Overcast. 

Nov.  22 

8 

a.  m. 

— 

7 

— 

2 

9 

-  42 

-266 

— 

37 

Clear. 

Nov.  23 

7  30 

a.  m. 

— 

11 

+ 

4 

14 

-  40 

-268 

— 

21 

Overcast. 

Nov.  24 

7  30 

a.  m. 

— 

2 

+ 

15 

13 

-  50 

-265 

— 

23 

Do. 

2 

p.  m. 

+ 

4 

+ 

30 

-  42 

-258 

- 

8 

Clear. 

Nov.  25 

7 

a.  m. 

4 

3 

5 

-  75 

-267 

— 

60 

Do. 

2 

p.  m. 

+ 

5 

+ 

25 

13 

-  51 

-252 

— 

13 

Hazy.  Long  branch 

reset  at  0. 

Nov.  26 

m. 

+ 

8 

+ 

12 

14 

-  59 

-  22 

— 

9 

Hazy. 

Nov.  27 

8 

a.  m. 

— 

3 

— 

3 

5 

-  83 

-  38 

— 

49 

Clear. 

Nov.  28 

8 

a.  m. 

— 

2 

+ 

6 

8 

-  83 

-  47 

— 

42 

Do. 

GASES,  TENSION,  SUCTION  AND  PRESSURE  IN  JUGLANS.  103 

COMPOSITION  OF  INTERNAL  GASES  OF  JUGLANS. 

In  order  to  obtain  a  sample  of  the  gases  in  the  vessels  of  the  older 
wood  a  radial  bore  was  made  into  the  trunk  of  the  tree  to  which  6 
manometers,  a  dendrograph  and  a  thermometer  were  affixed.  The 
cavity  was  12  cm.  in  depth,  1  cm.  in  diameter  and  extended  toward 
the  center  on  the  opposite  side,  and  25  cm.  below  the  tangential  bore. 
The  gas  receiver  and  column  of  mercury  for  producing  suction  were 
attached  as  in  figure  10.  The  preparation  was  completed  at  3  p.  m. 
on  October  19,  1925,  and  the  column  was  set  to  give  a  suction  of  about 
—  500  mm.  Hg.  At  4  p.  m.  100  ml.  of  gas  had  been  drawn  out.  At 
4  p.  m.  on  the  20th  about  200  ml.  gas  had  been  drawn  out,  and  an 
analysis  was  made  with  the  following  results:  C02:  10.62  p.  ct.; 
10.63  p.  ct.  O:  9.96  p.  ct.;  9.94  p.  ct.  N:  79.42  p.  ct. 

A  section  of  the  exhausting  tube  of  rubber  had  been  left  uncoated 
and,  as  a  consequence,  some  C02  was  lost  by  diffusion;  this  error 
was  rectified  in  a  second  extraction  from  the  same  bore  which  showed 
the  following  composition:  C02:  12.13  p.  ct.;  12.20  p.  ct.  02:  8.41 
p.  ct.;  8.41  p.  ct.  N:  79.43  p.  ct.;  79.39  p.  ct. 

It  is  evident  that  gases  may  diffuse  but  slowly  and  against  great 
resistance  to  allow  the  accumulation  of  proportions  of  C02  six-hundred 
times  as  great  as  in  the  air. 

The  activity  of  the  living  cells  was  not  as  great  at  this  time  as 
earlier  in  the  season.  Growth  had  ceased  and  the  leaves  were  begin¬ 
ning  to  turn  yellow  and  fall  off. 

CONDITIONS  AFFECTING  TENSION,  SUCTION  AND 

PRESSURE  IN  JUGLANS. 

The  experiments  by  which  the  measurements  given  in  the  preceding 
pages  were  derived  included  arrangements  of  manometers  by  which 
pressures  in  the  outer  and  inner  wood,  in  a  short  stub  of  a  branch,  at 
the  end  of  a  long  branch  with  many  leafy  branchlets,  at  the  end  of 
a  heavy  root  with  many  laterals  at  a  distance  of  1.6  meters  from  the 
base  of  the  trunk,  and  in  the  separated  part  of  this  root. 

Such  measurements  are  usually  designated  as  showing  “  sap- 
pressure/7  and  “negative-pressure,”  but  they  may  be  more  accurately 
termed  “suction”  and  exudation  pressure  of  gases  and  liquids  in  the 
trunk.  It  has  already  been  made  plain  in  preceding  discussions  that 
suction  may  be  due  to  capillarity  in  vessels  in  the  wood  cells,  to  the 
absorption  of  liquids  by  living  cells  and  to  connection  with  reservoirs 
of  gases  under  pressures  less  than  atmospheric  in  the  older  wood  of 
the  central  part  of  the  trunk. 

Experimentors  have  hitherto  agreed  in  concluding  that  no  corre¬ 
lation  could  be  established  between  manometric  measurements  in 
different  bores  or  on  stumps  no  matter  how  near  together  or  widely 


104 


HYDROSTATIC  SYSTEM  OF  TREES. 


separated  they  might  be.  Such  a  condition  may  be  safely  attributed 
to  the  fact  that  nearly  all  observations  have  been  made  in  such  manner 
that  it  is  impossible  to  determine  what  connections  were  made  with 
the  various  parts  of  the  hydrostatic  system  of  the  tree  as  illustrated 
in  figure  1. 

Attempts  to  define  “  periodicities  ”  in  pressures  have  also  failed. 
The  tensions  and  pressures  in  the  trunk  are  affected  primarily  by 
the  balance  between  water-loss  and  water-intake.  A  wide  variety  of 
factors  influence  the  included  processes.  In  addition,  temperature 


Fig.  20. — Graphs  of  suction,  etc.,  of  Juglans.  A,  course  of  water-loss  from  Livingston 
evaporimeter;  B,  temperature  of  outer  layer  of  wood;  C,  dendrographic  record  of 
variation  in  diameter  of  the  trunk;  D,  variations  in  suction  in  tangential  bore,  an  increase 
in  the  period  of  high  being  recorded ;  E,  variations  in  suction  of  radial  bore,  a  decrease 
at  time  of  highest  temperature  and  greatest  expansion  of  internal  gases. 

doubtless  constitutes  an  important  factor  in  modifying  pressure  and 
solubility  of  the  gases.  Simple  or  direct  concurrence  of  manometric 
readings  from  bores  or  stumps  are,  therefore,  not  to  be  expected. 

It  is  only  when  the  nature  of  the  connections  made  for  each  instru¬ 
ment  are  taken  into  account  that  some  order  appears  in  the  chaos. 
It  can  not  be  claimed  that  an  adequate  explanation  can  be  made  of 
all  the  phenomena  implied  in  the  preceding  measurements.  This 
could  only  be  done  by  the  maintenance  of  a  battery  of  instruments 
upon  such  a  large  number  of  trees  that  individuals  could  be  taken 
down  for  dissection  at  frequent  intervals.  Minute  records  of  stomatal 


TENSION,  SUCTION,  AND  PRESSURE  IN  JUGLANS. 


105 


program  and  numerous  gas  analyses,  with  meteorological  and  soil 
studies,  would  also  be  necessary. 

The  work  described,  however,  establishes  the  principal  features  of 
the  hydrostatic  system  and  delineates  the  features  of  its  action.  It 
is  thus  made  possible  upon  the  basis  of  the  conceptions  furnished  to 
make  detailed  studies  of  any  feature  of  the  sap  or  the  accessory  gaseous 
system  that  may  seem  desirable. 

In  the  more  primitive  system  of  the  conifers,  and  in  a  tree  like  the 
Monterey  pine,  it  is  possible  to  drive  tangential  bores  in  wood  in 
which  comparatively  little  air  is  included.  It  may  be  safely  taken 
for  granted  that  any  bore  a  few  centimeters  in  depth  with  a  diameter 
of  8  or  10  mm.  made  in  the  trunk  of  a  walnut  will  cut  many  vessels 


M.  M.  M.  M.  M.  M.  M.  M. 


MT  MT.  MT.  MT.  MT.  MT.  MT 


Fig.  21. — Dendrograph  records  of  Juglans  major.  The  week  beginning  July  6  was  char¬ 
acterized  by  a  wide  range  of  daily  variation  in  diameter  with  some  permanent  increase 
due  to  growth.  High  positive  pressures  in  the  tangential  bore,  low  suction  in  the  short 
stub  of  a  branch  and  high  suction  pressures  in  the  long  branch  were  observed.  The  week, 
beginning  August  17  (July  17  by  mistake  in  lettering)  was  characterized  by  alternations 
from  suction  to  exudation  in  the  tangential  bore,  high  temperatures,  abrupt  changes 
in  diameter,  and  suction  in  radial  bore  and  in  branches.  Growth  had  ceased.  Some 
positive  pressures  were  recorded  in  the  tangential  bore  in  the  week  beginning  Sep¬ 
tember  14.  Suction  was  high  in  other  manometers  on  trunk  and  branches.  Daily 
variation  in  diameter  was  near  the  minimum.  High  temperatures  were  observed  in 
the  week  beginning  October  12.  Daily  variation  in  diameter  was  near  the  minimum. 
Some  exudation  pressure  in  the  tangential  bore  and  at  cut  end  of  a  root.  Suction  in 
radial  bore  and  in  branches. 

containing  gases.  The  results  of  the  analyses  show  that  carbon 
dioxide  sustains  a  high  partial  pressure  in  these  gases.  When  a  bore 
connects  with  the  gas-filled  layers  the  water  introduced  dissolves 
these  gases  unequally,  but  to  a  total  which  must  be  of  some  conse¬ 
quence.  The  application  of  water  to  the  exposed  ends  of  the  wood 
in  a  bore  or  at  the  cut  end  of  a  branch  would  connect  directly  with  the 
water-column  in  the  sap  conduits,  so  that  variations  in  tension  in 
this  layer  would  be  registered  directly  and  in  a  manner  capable  of 
simple  interpretation  after  the  initial  adjustment  is  made.  The 
manometer  should  within  a  day  or  two  register  the  state  of  tension, 
or  at  least  the  course  of  changes  in  tension.  Accuracy  will  depend  on 
how  exclusively  connection  is  made  with  the  sap-filled  elements, 
tracheids,  and  trachea)  and  to  what  extent  liquid  and  gas  replace  each 
other  in  the  elongated  conducting  elements.  It  might  be  expected, 


106 


HYDROSTATIC  SYSTEM  OF  TREES. 


under  conditions  in  which  the  draft  on  the  water-column  was  greatest, 
that  the  liquid  would  be  exhausted  in  some  of  the  larger  vessels,  at 
a  time  when  a  shrinkage  of  the  trunk  is  taking  place. 

Diminution  of  the  rate  of  water-loss  would  naturally  be  followed 
by  replacement  of  gases  by  liquid  in  these  vessels,  if  a  supply  is  avail¬ 
able.  Now  when  water  is  applied  to  such  tracts  capillary  action 
would  result  in  filling  all  connecting  vessels,  as  has  been  demonstrated 
in  the  oak.  Tracheids  would  also  be  injected.  This  process  draws 
water  from  the  connecting  tube  of  the  manometer  which  causes  a 
registration  of  “  negative  pressure  ’ 7  or  suction,  and  which  is  difficult  to 
separate  from  the  effects  of  less  than  atmospheric  pressure  in  the  gases. 

It  being  important  to  determine  the  extent  to  which  stomatal 
action  might  affect  the  rate  of  water-loss  and  the  tension  in  the  sap- 
column,  an  examination  of  the  action  of  these  organs  was  made  by 
Professor  F.  E.  Lloyd,  who  has  kindly  furnished  the  following  notes 
concerning  their  behavior  in  August  when  the  leaves  were  fully 
mature  and  slightly  yellowish  and  the  soil-moisture  had  fallen  to  its 
minimum.  These  observations  were  made  August  28,  1925,  coinci¬ 
dent  with  the  intensive  observations  made  with  the  manometers. 

Material  for  the  study  of  the  behavior  of  the  stomata  with  respect  to  their 
daily  march  of  opening  and  closing  was  obtained  by  stripping  and  by  slicing 
of  thin  pieces  of  epidermis  and  plunging  the  samples  into  absolute  alcohol 
(the  Lloyd  method).  It  should  be  noted  that  the  epidermis  of  this  tree  is 
quite  difficult  to  strip,  only  narrow  fringes  of  epidermis  being  obtained. 
The  areas  for  unobstructed  view  of  the  stomata  were,  therefore,  very  small 
and  seldom  contained  more  than  10  or  15  stomata  in  any  one  area  of  free 
epidermis.  The  examination  of  such  material  affords  the  following  data: 


Table  23. 


Date. 

Time. 

Average  width  of 
open  stomata 
pores. 

Maximum  opening 
and  width. 

Effective  width. 

1925 

M 

M 

Aug.  27 

10b15m 

a.  m. 

2 

4 

1 

1.5 

2 

0.75 

27 

2 

p.  m. 

1.5 

2 

0.3 

27 

7 

p.  m. 

1 

1 

nearly  0 

28 

4 

a.  m. 

1.5 

2 

0.75 

28 

6 

a.  m. 

1.5 

2 

0.2 

28 

7  30 

a.  m. 

1.5 

2 

0.2 

28 

9 

a.  m. 

1.5 

2 

1 

28 

11  30 

a.  in. 

0 

1.5 

0 

28 

4 

p.  m. 

0 

1 

0 

It  will  be  noted  that  the  above  data  indicate  a  rather  meager  mobility, 
and  the  natural  question  arose  if  these  represented  the  limits  of  possibility 
in  this  regard.  It  was,  therefore,  necessary  to  determine,  if  possible,  the 
extreme  limits  of  mobility.  In  order  to  do  this,  pieces  of  living  epidermis 
were  floated  upon  distilled  water.  Control  material  from  identical  leaves 
were  placed  in  absolute  alcohol  at  once,  this  showing  only  a  very  few  stomata 
open,  the  maximum  width  of  pore  2ju.  The  material  floated  on  distilled 


TENSION,  SUCTION,  AND  PRESSURE  IN  JUGLANS. 


107 


water  was  fixed  in  alcohol  at  the  close  of  2  days,  and  showed  upon  examina¬ 
tion  that  only  about  15  per  cent  of  the  stomata  were  now  closed,  while  the 
open  stomata  showed  a  range  of  pore  width  of  1  to  5ju,  the  average  width  for 
the  80  per  cent  open  stomata  being  about  3/z.  The  difference  between  the 
stomata  on  the  tree  and  those  subjected  to  distilled  water  was  striking  and 
left  no  doubt  that  the  limiting  factor  for  stomata  behavior  on  the  tree  lay  not 
in  their  immobility,  but  rather  in  the  external  factors,  which  likely  enough 
was  the  dryness  of  the  soil.  On  this  supposition  the  stomata  of  a  succulent 
Pelargonium  and  Vinca,  growing  in  dry  sandy  soil,  and  of  Helianthus  annuus, 
growing  in  well-watered  soil,  were  examined,  although  there  was  no  doubt 
that  the  Vinca  and  Pelargonium  stomata  had  a  high  degree  of  mobility,  as 
shown  by  distilled  water.  It  was  found  that  they  were  for  the  most  part 
only  narrowly  open  with  a  maximum  of  about  2/x  for  both  young  and  old 
leaves,  while  the  stomata  of  the  sunflower  showed  a  very  ample  movement 
amounting  to  a  general  aperture  of  from  5  to  7/z  width.  We  may,  there¬ 
fore,  in  general  conclude  that  the  stomata  of  Juglan  show,  during  a  preva¬ 
lence  of  soil  and  other  conditions  obtaining  at  the  time  of  the  examination, 
a  minor  amplitude  of  movement.  It  may,  however,  be  noted  in  this  con¬ 
nection  that  on  sunshiny  days  during  the  middle  of  the  day,  the  leaves  show 
a  net  water-loss  as  indicated  by  their  lack  of  crispness,  quite  notable  when 
epidermis  is  being  stripped. 

It  would  appear,  therefore,  that  the  activity  of  the  stomatal  cells, 
in  regulating  the  slits  through  which  water  vapor  passes  as  it  comes 
free  from  the  menisci  in  the  transpiring  cells,  is  by  no  means  so  definite 
as  the  reversible  variations  in  the  thickness  of  the  sap-carrying  layers 
which  is  correlated  with  tension  in  the  water-column  in  these  layers. 

The  dendrographic  record  was  begun  in  June,  about  30  or  40  days 
after  enlargement  of  the  trunk  had  set  in.  Additions  to  the  diameter 
continued  until  late  in  September,  thus  extending  over  a  period  which 
may  be  estimated  at  130  to  140  days.  The  minimum  for  this  tree  is 
95  days  and  the  maximum  165  days,  and  the  present  observations 
were  therefore  made  in  a  season  near  the  mean  for  the  locality. 

Contraction  of  the  stem  began  at  daybreak  on  clear  days  early  in 
the  season  and  continued  for  about  6  to  8  hours  (see  fig.  21).  Shortly 
after  mid-day,  the  minimum  was  reached,  after  which  enlargement 
began  at  a  rate  less  than  that  of  contraction,  which  decreased  until 
daybreak  when  the  reversal  occurred.  As  will  be  shown  in  the  review 
of  the  detailed  records  from  the  manometers,  the  morning  period  or 
dawn  was  marked  by  the  prevalence  of  the  greatest  positive  or  exuda¬ 
tion  pressures,  indicative  of  the  least  tensions  in  the  sap-column,  and 
by  the  highest  suction  in  the  gas-filled  layers.  Coincidental  with 
contraction  of  the  wood,  and  supposedly  causally  related  to  it,  was 
increased  tension  of  the  sap-column  by  which  positive  pressure  dis¬ 
appeared  and  suction  began.  At  the  same  time  suction  became  less 
in  bores  penetrating  the  inner  wood  containing  much  gas  in  which 
carbon  dioxide  was  present  in  proportions  as  high  as  12  per  cent. 
These  reactions  characterize  a  growing  trunk  at  the  season  when 
soil-moisture  is  adequate,  relative  humidity  is  high  at  night,  while  a 


108 


HYDROSTATIC  SYSTEM  OF  TREES. 


clear  sky  and  sunshine  with  a  rise  of  8°  to  12°  C.  in  the  temperature  of 
the  outer  tissues  facilitate  transpiration.  These  simple  conditions 
of  the  environic  complex  were  presented  on  a  few  days  only.  Low 
heavy  fogs  caused  dripping  foliage  in  the  early  part  of  a  large  pro¬ 
portion  of  the  days,  while  the  sky  was  overcast  by  high  fogs  on  many. 

Contraction  of  the  stem  becomes  very  abrupt  in  late  August,  after 
which  period  the  amplitude  of  shrinkage  lessens. 

Any  explanation  to  be  adequate  must,  of  course,  account  for  varia¬ 
tions  and  conditions  of  tension  under  all  circumstances.  The  basis 
of  such  explanations,  however,  may  be  most  easily  found  by  a  con¬ 
sideration  of  selected  “cases”  or  “runs”  of  the  variations  under 
simple  combinations  in  which  the  greatest  number  of  agencies  affect 
tension  or  pressure  concurrently,  or  harmoniously. 

An  inspection  of  the  extensive  records  given  on  the  preceding  pages 
will  confirm  the  statement  that  in  any  tapping  of  the  tissues  of  the 
trunk  of  Juglans  with  a  fitting  of  a  manometer  which  applies  water 
to  the  cut  surfaces  is  followed  directly  by  suction,  which  may  be  due 
to  absorption  by  living  cells,  capillarity  of  vessels  and  wood,  or  the 
pull  of  a  sap-column  under  tension.  All  of  these  conditions  operate 
in  varying  proportions  in  almost  any  test. 

Suction  and  Pressure  in  a  Tangential  Bore. 

Figure  19  C. 

At  the  beginning,  May  17,  1925,  instruments  were  applied  to  a 
tangential  bore  and  to  the  end  of  a  long  branch  of  Juglans .  Suction 
showed  for  7  days  in  the  tangential  bore,  the  amount  varying  between 
0  and  —20  mm.  Hg.,  with  some  air  forced  or  drawn  into  the  bore, 
presumably  from  vessels  tapped.  During  the  same  period,  the  high 
initial  suction  in  the  branch  varied  from  5  to  80  mm.  Hg.,  with  much 
air  coming  from  the  vessels  and  medulla. 

Eight  days  after  the  manometer  had  been  fitted,  a  still  of  the  pres¬ 
sures  or  tensions  was  noticeable  which  index  the  nature  of  the  dom¬ 
inant  agencies  in  each  case  unmistakably.  Exudation  pressures 
began  to  show  in  the  tangential  bore,  which  reached  a  maximum  of 
+ 176  mm.  Hg.  early  in  July,  at  the  height  of  the  growing  season,  but 
which  lessened  and  alternated  with  suction  amounting  to  —110 
mm.  Hg.  early  in  June.  These  extremes  came  within  the  period 
in  which  reversible  variations  were  greatest.  The  reduction  of  pres¬ 
sure  and  the  appearance  of  suction  such  as  was  shown  May  26  and 
31,  June  4,  5,  24,  26,  July  4,  5,  11,  13,  15,  16,  17,  etc.,  was  under 
conditions  in  which  transpiration  would  be  increasing.  The  reverse 
variation  by  which  suction  was  lessened  and  positive  pressures  ap¬ 
peared  wras  under  conditions  which  would  check  water-loss,  as  illus¬ 
trated  by  the  records  of  May  26  and  27,  30  and  31,  June  13  and  14, 
15  and  17,  25  and  27,  July  11-16,  24-25,  etc. 


TENSION,  SUCTION,  AND  PRESSURE  IN  JUGLANS. 


109 


The  meteorological  notations  pertain  to  the  hour  at  which  the 
manometric  reading  was  made,  and  the  pressure  or  suction  may 
have  been  determined  almost  wholly  by  conditions  of  the  previous 
night  or  day.  Thus  change  from  pressure  of  +48  to  suction  —  25  in 
the  forenoon  of  May  27-29  is  seen  to  be  due  to  a  steep  rise  and  high 
maximum  temperature.  Suction  on  May  30-31  was  a  consequence 
of  high  temperature  with  light  showers,  which  as  soon  as  the  rain 
ceased  rose  to  —100  mm.  Hg.  This  condition  continued  for  several 
days,  when  it  may  be  seen  that  fog  or  clouds  lessened  suction. 

It  is  further  notable  that  but  little  air  came  from  this  tangential 
bore  and  that  the  range  of  variation  decreased  toward  the  end  of  the 
season.  The  entire  record  seems  clearly  explainable  on  the  basis 
of  a  water-column  under  tension,  at  times  presumably  from  the  trans- 
piratory  pull  from  the  leaves  and  at  other  times  under  compression 
from  the  action  of  living  cells.  The  seat  of  such  pressure,  ordinarily 
termed  “ root-pressure/’  is  not  easily  to  be  fixed  upon.  It  may  not 
be  attributed  to  temperature  effects  on  included  gases,  as  it  is  greatest 
concurrently  with  the  greatest  diameter  at  the  time  of  lowest  temper¬ 
ature.  It  may  only  be  safely  assigned  to  the  action  of  living  cells  of 
the  rays  or  xylem,  or  to  the  endodermal  mechanism.  The  essential 
activity  of  these  cells  would  continue  at  a  varying  rate  as  of  osmosis 
and  hydration  affected  by  temperatures,  but  the  actual  pressure  or 
tension  registered  would  simply  indicate  the  balance  between  such 
action  and  the  pull  from  the  leaves. 

Suction  and  Pressure  in  a  Radial  Bore. 

The  radial  bore  was  not  made  until  much  later  than  the  tangential 
one  in  the  newer  wood,  but  the  essential  differences  between  the 
complex  of  agencies  operative  here  and  in  the  tangential  cavity  are 
apparent.  Chief  among  these  is  the  fact  that  no  positive  or  exudation 
pressure  was  shown  until  November.  The  tube  fitted  to  the  bore 
did  not  extend  beyond  all  elements  carrying  the  sap-column,  and  the 
capillary  injection  from  the  bore  doubtless  made  some  liquid  connec¬ 
tion  with  the  ascending  current.  The  increased  transpiration  would, 
therefore,  be  expected  to  cause  some  increase  in  the  suction  in  the 
mid-day  period,  and  this  is  well  illustrated  in  the  first  few  days  of  the 
record.  This  would  be  especially  true  on  clear  days.  The  gradual 
increase  in  suction,  which  was  seen  here  as  well  as  in  all  bores  con¬ 
necting  with  old  wood,  obscures  the  daily  variation  to  some  extent. 
Such  an  increase  might  not  reach  its  maximum  for  a  month  after  the 
column  in  the  manometer  was  set  to  0.  Some  deviations  from  the 
course  of  daily  action  by  which  the  suction  was  least  at  mid-day 
might  also  be  attributed  to  gases  coming  from  the  wood  or  from  the 
atmosphere  by  reason  of  minute  leaks  in  the  fittings.  Clearly  defined 
action  is  illustrated  by  the  records  of  August  11,  12,  13,  14,  18,  19,  20, 


110 


HYDROSTATIC  SYSTEM  OF  TREES. 


22,  25,  26,  September  8,  9,  21,  24,  October  4,  5,  6,  7,  8,  9,  12,  24,  etc., 
in  which  transpiration  and  contraction  of  the  stem  have  a  mid-day 
maximum  coincident  with  the  greatest  suction  pressure  or  tension  in 
the  moving  water-column. 

The  diminution  of  suction  in  the  central  gas-filled  wood  at  the 
time  of  greatest  water-loss  has  been  one  of  the  unexpected  features  of 
the  extensive  results  described  in  this  paper;  especially  since  suction 
likewise  reaches  its  maximum  at  the  beginning  of  the  day  when 
transpiration  is  least.  Direct  connection  of  this  kind  is  to  be  seen 
in  the  detailed  records  of  August  27  and  28,  although  here,  as  else¬ 
where,  irregularities  appear.  Late  in  the  season  when  soil-moisture 
was  low  and  growth  had  ceased  the  mid-day  decrease  of  suction  was  an 
invariable  feature  of  a  clear  day,  and  was  even  seen  on  cloudy  days 
in  which  of  course  transpiration  was  something  greater  than  at  night. 

The  only  agency,  the  variations  of  which  run  parallel  in  such 
manner  as  to  suggest  causal  relations,  is  that  of  temperature.  The 
records  were  obtained  from  a  mercurial  thermometer  thrust  tan¬ 
gentially  into  the  new  wood  of  the  trunk,  early  in  July.  The  forma¬ 
tion  of  some  new  wood  gave  the  bulb  a  relatively  deeper  position  before 
the  end  of  the  season.  The  actual  temperatures  of  the  gas-filled 
wmod  would,  of  course,  be  neither  so  high  nor  so  low  as  those  of  the 
outer  wood  from  which  the  records  were  made,  and  the  variations 
would  lag  behind  those  shown  by  the  thermometer.  The  volume  of 
the  gas  would  vary  according  to  the  formula  V+  =  Vo  (1+atm.)  at 
constant  pressures,  or  approximately  1/273  for  1°  variation,  this 
coefficient  being  slightly  greater  for  C02  than  for  oxygen  and  nitrogen. 
The  variations  in  volume  run  nearly  parallel  with  those  of  pressure 
in  the  range  of  these  observations.  Volume  of  the  gases  would  also 
be  modified  to  some  extent  by  their  solubility  in  the  sap  of  the  outer 
wood,  which  would  run  inversely  to  the  temperature  and  thus  ac¬ 
centuate  the  changes  in  volume  of  the  gas. 

If  the  record  be  examined  with  regard  to  this  matter  it  will  be  seen 
that  some  correspondence  prevails  between  the  range  of  variation  in 
temperature  and  of  suction,  but  the  correlation  is  by  no  means  high 
or  complete.  Thus  on  August  13  the  temperatures  morning,  noon 
and  evening  are  13°,  18°,  and  18°  C.,  the  suction  being  51,  48  and  54 
mm.  Hg. ;  likewise,  on  August  17  temperatures  were  15°,  20°  and  19°  C., 
and  suction  51,  56,  and  59  mm.  Hg.  Similar  records  were  made  for 
August  18  and  19.  The  detailed  observations  of  August  27  likewise 
fail  to  show  direct  relations  between  changes  in  gas  volume  and  suc¬ 
tion.  The  temperature  of  the  trunk  remained  unchanged  at  10°  C. 
from  sunset  of  August  27  to  8  a.  m.  on  the  28th,  and  during  this  12- 
hour  period  suction  varied  as  follows:  —78,  81,  79,  80,  78  and  74 
mm.  Hg.  The  daily  rise  in  temperature  gave  readings  of  12°,  13°, 
15°,  16°  and  18°  C.,  a  steady  rise  until  4  p.  m.,  the  suction  varying 


TENSION,  SUCTION,  AND  PRESSURE  IN  JUGLANS. 


Ill 


at  the  same  time  as  follows:  71,  68,  69,  72,  75  mm.  Hg.  However,  at 
9  p.  m.  suction  has  decreased  to  81  mm.  with  a  temperature  of  12°  C. 
Later  in  the  season  suction  appeared  to  follow  variations  determined 
by  temperature,  being  greatest  in  the  morning,  decreasing  in  the 
warmer  mid-day  period  and  increasing  again  with  the  decreasing 
volume  of  cooling  gases  in  the  evening.  This  is  well  illustrated  by  the 
records  of  September  8,  14,  21,  22,  23,  24,  October  7,  10,  24,  and  No¬ 
vember  15. 

Here  as  in  all  other  preparations  it  can  not  be  assumed  that  the 
radial  bore  taps  only  the  gas-filled  wood.  The  liquid  from  the  bore 
injects  the  tracts  which  are  cut  across,  and  it  is  highly  probable 
that  connection  is  made  with  the  ascending  column  under  tension. 
The  records  cited  make  it  obvious  that  the  changes  in  volume  of  the 
gases  included  in  the  old  wood  of  the  tree  determine  the  suction  pres¬ 
sure  in  radial  or  deep  bores  in  trunks. 

A  final  record,  especially  pertinent  to  the  question,  was  made  on 
November  19,  as  the  manuscript  for  this  paper  was  being  completed. 
Suction  had  come  down  to  0  with  a  rise  of  temperature  from  7°  to 
18°  C.  in  about  5  hours  on  the  15th,  and  several  readings  were  made  on 
the  19th,  on  which  day  the  cool  morning  was  followed  by  a  warm 
clear  mid-day  without  wind.  Suction  was  equivalent  to  9  mm.  Hg. 
at  7h30m  a.  m.,  which  was  reduced  and  a  pressure  of  +14  mm.  Hg.  set 
up  in  4  hours,  an  increase  to  +15  mm.  Hg.  taking  place  by  2  p.  m.,  at 
which  time  the  outer  layer  of  the  trunk  had  a  temperature  of  22°  C. 
These  were  the  first  positive  pressures  from  a  radial  bore  during  the 
season. 

At  no  time  were  any  notable  amounts  of  suction  or  pressure  recorded 
by  air-filled  manometers  (see  record  of  oak,  pp.  80,  81,  and  pine  No.  6, 
page  36).  An  old  radial  bore  from  which  gas  sample  had  been  taken 
3  weeks  earlier  was  emptied  of  mercury,  cleaned  and  connected  with 
an  air-filled  manometer  on  November  14.  Within  an  hour  a  suction 
of  —5  mm.  Hg.  was  registered  at  a  time  when  the  radial  bore  was 
showing  a  suction  of  —8  mm.  Hg.  in  a  w'ater-mercury  filled  instru¬ 
ment.  At  noon  on  this  day  (November  19)  positive  pressure  had 
caused  some  air  to  escape,  and  at  2  p.  m.  a  suction  of  —5  mm.  Hg. 
was  registered.  The  maximum  suction  registered  by  this  radial  bore 
was  92  mm.  Hg.  =0.12  atm.  at  the  end  of  August,  after  which  time 
an  irregular  decrease  followed,  which  on  November  19  was  transformed 
to  positive  pressure  as  noted. 

Suction  in  Short  Stub  of  Branch. 

Figure  16  B. 

Stub  of  a  branch  20  cm.  long  and  15  mm.  in  diameter  at  the  cut 
end,  arising  from  the  trunk  25  cm.  above  the  radial  bore  at  an  angle 
of  35°  from  it,  was  fitted  with  a  manometer  on  June  19,  while  vigorous 


112 


HYDROSTATIC  SYSTEM  OF  TREES. 


growth  was  in  progress.  It  is  to  be  noted  that  such  a  structure  com¬ 
municated  with  the  water-column  under  tension  in  the  outer  layers 
of  the  trunk  and  also  with  the  air-filled  wood  of  the  interior.  To 
what  extent  capillarity  caused  the  central  wood  and  disintegrating 
medulla  to  be  filled  with  water  could  not  be  determined.  It  is  obvious 
however,  that  the  readings  of  this  instrument  would  be  the  resultant 
of  the  tension  on  the  water-column  and  of  the  expansion  and  contrac¬ 
tion  of  the  gas-filled  wood.  As  in  all  preparations  connecting  with 
old  wood,  much  air  was  drawn  out  from  time  to  time.  The  amount 
of  suction  rose  irregularly  for  2  days,  when  air  was  released  and  the 
instrument  reset  to  0.  An  irregular  increase  carried  suction  to  —93 
mm.  Hg.  4  days  later.  The  mid-day  decrease  and  nightly  increase 
is  plainly  to  be  noted.  On  July  1  detailed  readings  showed  suction 
diminishing  to  0  at  10  a.  m.,  being  converted  to  a  positive  pressure  of 
+3  mm.  at  mid-day,  followed  by  suction  reaching  —26  mm.  Hg.  at 
8  p.  m.  A  similar  variation  was  less  marked  on  the  following  day 
which  was  equable  and  foggy.  This  type  of  variation  was  seen  on 
several  days  following.  High  temperatures  on  July  11  lessened  suc¬ 
tion,  producing  positive  pressure  on  the  12th  and  13th. 

After  this  time  it  would  seem  as  if  connection  with  the  moving 
water-column  under  tension  had  been  restricted,  as  in  the  following 
month  the  mid-day  decrease  with  increase  at  night  is  discernible  on 
16  days — not  more  than  one  or  two  observations  having  been  made  on 
many  of  the  other  days.  Similar  records  run  to  the  close  of  the  obser¬ 
vations.  Maxima  of  suction  of  — 103  mm.  Hg.  June  19;  93  on  the  27th; 
—  36  on  July  9;  —48,  July  16;  —60,  July  20;  —71,  July  24;  —79,  July 
28;  —83,  August  2;  —63,  August  14;  —75,  August  19  and  20;  —66, 
August  27;  —81,  September  2;  — 114,  September  14;  — 134,  September 
24;  —94,  October  8;  —123,  October  18;  —150,  October  28;  —160, 
November  5;  —162,  November  14,  constituting  a  seasonal  variation 
from  high  maxima  in  June,  lesser  maxima  in  July  and  August,  and 
increasing  maxima  in  September  and  October  and  November.  The 
highest  —162  mm.  Hg.  would  be  equivalent  to  0.2  atmosphere.  This 
suction  was  at  the  minimum  temperature  of  4°  C.,  following  a  suction 
of  — 160  mm.  Hg.  on  the  previous  day  at  a  temperature  of  6°  C.  The 
conclusion  that  temperature  determining  the  volume  and  pressure  of 
the  gas  in  the  vessels  and  old  wood  of  the  trunk  is  the  principal 
factor  in  suction,  and  pressure  of  stubs  of  branches  seems  unescapable. 
The  relation  is  even  more  clearly  marked  than  in  radial  bores,  although 
this  may  be  partly  due  to  the  manner  in  which  the  instruments  were 
fitted. 


Suction  at  End  of  Long  Leafy  Branch. 

Figure  19  D. 

A  manometer  was  fitted  by  a  clamped  section  of  pressure  tubing  to 
the  end  of  a  leafy  branch  4  meters  long,  arising  from  near  the  base  of 
the  trunk  early  in  the  season  before  growth  had  reached  a  maximum 


113 


TENSION,  SUCTION,  AND  PRESSURE  IN  JUGLANS. 

rate.  Much  air  was  drawn  out  during  the  first  week,  after  which  an 
irregular  increase  in  suction  took  place  which  reached  a  maximum  of 
—  84  mm.  Hg.  on  June  17,  when  air  was  drawn  out  and  the  instrument 
was  reset  at  0.  A  maximum  of  177  was  reached  on  July  9,  and  suc¬ 
tion  varied  about  a  high  level  until  near  the  end  of  the  month,  when 
it  was  necessary  to  release  air  from  the  instrument  and  reset  to  0. 
Suction  varied  below  —174  for  a  month  when  air  was  released  and 
the  column  set  to  0.  Then  followed  a  period  of  wide  variation  below 
— 108  mm.  Hg.  On  September  9,  near  the  end  of  the  growing  season, 
an  irregular  rise  took  place,  which  reached  a  maximum  of  —182  mm. 
on  September  24  and  —192  on  September  29.  The  column  was  again 
reset  at  0.  The  characteristic  irregular  increase  in  suction  reached 
maxima  of  —267  mm.  late  in  November. 

If  detailed  daily  records  are  examined,  it  is  to  be  seen  that  not 
much  variation  took  place  on  cloudy  or  rainy  days.  It  is  apparent, 
however,  that  suction  sometimes  decreased  throughout  the  day,  as 
illustrated  by  the  records  of  June  13,  17,  22,  24,  July  7,  11,  13,  14, 
and  many  others.  The  record  of  July  1  is  a  notable  illustration  of 
increase  in  suction  accompanying  a  fog  in  the  afternoon.  Later  in  the 
season  the  cycle  resembled  that  already  described  for  the  short  stub 
of  a  branch,  the  maximum  suction  of  morning  diminishing  to  a  maxi¬ 
mum  after  mid-day,  followed  by  a  rise  which  continued  until  the  fol¬ 
lowing  morning.  This  is  well  illustrated  by  the  detailed  readings 
made  on  August  27  and  28.  Early  in  the  season  the  variations  were 
of  a  character  implying  that  the  tension  of  the  water  column  in  the 
conducting  layers  was  an  important  factor  affecting  the  resultant 
suction.  Later  the  reactions  seemed  to  be  determined  by  the  tem¬ 
perature  changes  in  pressure  and  volume  of  the  gases  in  the  medulla 
and  older  wood.  Suction  at  times  amounted  to  0.34  atmospheres. 

Suction  and  Pressure  at  Terminal  or  Distal  End  of  an  Excised  Root. 

A  large  root  was  cut  at  a  distance  of  1.6  meters  from  the  base  of 
the  trunk  and  manometers  attached  to  the  exposed  ends.  This 
was  not  done  until  the  season  was  far  advanced  (Aug.  22),  and  the 
growth  period  was  coming  to  an  end.  The  soil-moisture  content  was 
low  and  the  leaves  were  taking  a  yellowish  tinge.  The  preparation 
was  one  in  which  all  parts  of  the  hydrostatic  machine  were  engaged. 
It  is  also  to  be  noted  that  while  the  instrument  would  show  the  pull 
from  the  tension  of  the  continuous  water-column,  lateral  roots  might 
furnish  solutions  to  the  main  root,  and  endodermal  action  might  well 
exert  a  pressure  distally  as  well  as  toward  and  upward  in  the  trunk. 

The  first  reaction  of  the  attached  root  was  one  of  absorption  and 
suction  during  the  first  24  hours.  Then  followed  a  period  in  which 
positive  pressure  in  the  mornings  was  followed  by  suction  after 
mid-day.  The  increase  in  volume  of  gases  in  the  wood  or  increased 


114 


HYDROSTATIC  SYSTEM  OF  TREES. 


endodermal  action  might  contribute  to  such  a  development  of  posi¬ 
tive  pressure  through  the  old  wood,  while  increased  tension  in  the 
water-column  would  tend  to  produce  a  suction  through  the  newer 
wood.  The  soil  at  a  depth  of  15  cm.  under  a  carpet  of  grasses  would 
not  warm  so  rapidly  as  the  trunk,  in  consequence  of  which  the  daily 
temperature  effect  would  come  later  than  in  the  stem.  The  latest 
pressure  effect  was  at  mid-day,  October  10.  Almost  every  clear  day 
thereafter  a  suction  diminishing  toward  mid-day  and  increasing  toward 
and  through  the  night  was  the  customary  occurrence.  With  the 
magnitude  of  pressures,  which  might  be  caused  by  osmotic  action 
across  the  endodermis,  unknown,  it  does  not  seem  profitable  to  carry 
the  analysis  further.  Positive  pressures  of  +16  mm.  Hg.  were  re¬ 
corded  when  the  test  was  first  set  up,  some  of  +12  and  +17  mm. 
(Sept.  2)  were  seen,  while  a  pressure  of  —27  mm.  was  registered  on 
October  4,  and  one  of  +5  mm.  on  October  13,  which  was  the  latest  record 
of  the  season.  Suction  at  times  as  high  as  —  32  mm.  Hg.  was  seen  in 
August,  but  did  not  exceed  —22  mm.  during  September.  The  range 
of  variation  became  high  in  October,  being  from  +5  to  —45  mm.,  but 
thereafter  fluctuated  between  —7  and  —56  mm.,  variations  of  about 
the  same  range  as  in  radial  bores  in  the  trunk. 

Suction  and  Pressure  in  the  Separated  Part  of  the  Root. 

The  records  obtained  from  the  separated  part  of  the  root  are  of 
interest  with  especial  reference  to  the  fact  that  tension  or  pull  from 
a  column  of  water  terminating  in  menisci  in  the  leaves  was  eliminated. 
At  the  same  time,  the  stoppage  of  the  diffusion  of  material  distally 
must  have  resulted  in  an  abnormal  condition  to  within  a  few  days. 
These  results  are  to  be  compared  with  similar  measures  on  separated 
roots  of  Pinus  (pp.  14-16). 

In  the  case  of  the  root  of  the  pine,  the  stump  of  the  separated 
root  showed  pressure  of  a  kind  that  has  been  identified  with  the 
exudation  of  resin  from  ruptured  canals  and  the  contraction  of  living 
cells  initially  hydrated  from  the  liquid  in  the  bore.  The  root  of  the 
walnut  developed  a  pressure  of  +156  mm.  Hg.  within  2  days,  and 
exhibited  diminishing  pressures  for  a  week.  The  balance  varied 
from  suction  to  pressure  for  a  day,  then  suction  prevailed  to  the  end 
of  the  experiment  late  in  November.  The  positive  pressures  were 
of  a  kind  suggestive  of  possible  hydration — dehydration  cycle  of 
living  cells  interrupting  what  may  have  been  a  continuous  endodermal 
performance.  Whether  or  not  this  performance  would  have  been 
repeated  if  a  section  of  the  root  had  been  cut  away,  as  had  been  seen 
by  many  observers,  is  not  known,  but  it  is  clear  that  deterioration  of 
the  terminal  rootlets  must  have  set  in  very  soon  after  the  initial 
operation. 


TENSION,  SUCTION,  AND  PRESSURE  IN  JUGLANS. 


115 


Rising  temperature  appeared  to  cause  increase  of  pressure  in  the 
initial  stage,  as  would  be  the  result  in  either  endodermal  or  simple 
hydration  reactions.  Later,  at  a  time  when  an  unknown  proportion 
of  the  root  was  dead,  the  familiar  cycle  of  maximum  suction  in  the 
morning,  diminishing  toward  mid-day,  and  increasing  with  falling 
temperature  was  seen  on  clear  days.  This  routine  was  disturbed  on 
cloudy  days  or  on  days  with  a  different  course  of  temperature.  Such 
reaction  would  seem  to  depend  almost  wholly  on  variations  in  volume 
of  gases  in  the  vessels  and  wood  cells. 

After  extended  records  had  been  made  the  root  was  taken  up 
(Nov.  20),  revealing  a  surprising  set  of  conditions.  All  of  the  rootlets 
were  dead  and  the  main  axis  showed  evidences  of  disintegration  to 
within  about  30  cm.  of  the  instrument.  Here  a  short  section  of 
wood,  of  the  color  of  “seasoned”  walnut  wood,  terminated  a  section 
of  the  root,  to  the  other  end  of  which  the  manometer  was  attached. 
The  woody  cylinder  was  about  20  mm.  in  diameter  and  the  bark 
2  mm.  in  thickness.  Both  regions  were  high  in  moisture  and  apparently 
retained  such  proportion  of  living  elements  as  give  much  the  appear¬ 
ance  of  a  normal  root.  The  section  protruded  one-third  its  length 
from  the  sandy  soil,  and  the  remainder  had  no  branches,  or  any 
absorbing  organs.  Exchanges  could  only  go  through  the  bark. 

The  uniformity  of  the  records  for  September,  October  and  Novem¬ 
ber,  and  the  condition  of  the  root,  support  the  inference  that  all  of 
the  root,  except  this  30  cm.  section,  died  at  the  end  of  the  initial  period, 
and  that  for  about  ten  weeks  the  measurements  may  be  taken  as 
showing  the  variations  in  volume  of  the  gases  included  in  the  wood. 

Positive  pressures  of  +156  mm.  Hg.  were  reached  within  2  days 
of  the  beginning,  and  continued  with  diminishing  value  for  a  week, 
which  probably  marks  the  beginning  of  deterioration  and  exhaustion 
of  carbohydrates.  After  this  the  short  section  of  root-surviving,  with 
its  capacity  for  exchanges  with  the  soil  reduced  to  a  very  low  rate, 
carried  a  stagnant  water-column  continuous  with  that  in  the  con¬ 
necting  tube  of  the  manometer.  The  variations  recorded  could  only 
be  attributed  to  changing  volumes  of  gas  under  the  influence  of  tem¬ 
peratures,  which  in  this  case  were  close  to  those  of  the  soil.  So 
clearly  is  the  case  as  described,  that  the  similarity  of  the  variations 
to  those  in  radial  bores  in  the  trunk  may  be  taken  as  confirming  in  a 
very  positive  manner  the  conclusion  that  these  variations  are  also  due 
to  changes  in  volume  and  pressure  of  gases  in  the  central  or  older  wood. 

Finally,  it  is  of  interest  to  note  that  suction  of  —198  mm.  Hg.  = 
0.26  atm.  was  measured,  and  that  during  the  concluding  period  of 
the  test  suction  ranged  from  0.17  to  0.2  atmospheres.  There  being  no 
intervention  of  tension  in  the  water-column  or  anything  but  very  slow 
exchanges  with  the  soil,  these  amounts  may  be  taken  as  expressing  the 
actual  conditions  of  gas-pressure  in  the  section. 


116 


HYDROSTATIC  SYSTEM  OF  TREES. 


DISCUSSION. 

The  conception  of  the  hydrostatic  system  of  the  tree  set  forth 
in  this  paper  includes  a  recognition  of  three  regions  mechanically 
distinct  in  the  trunk.  The  first  is  a  complete  cylindrical  shell  of  living 
cells  in  the  cambial  zone,  through  which  nothing  may  pass  except  by 
diffusion  through  protoplasm.  This  layer  is  continuous  with  the 
endodermis  in  the  roots  and  with  the  cells  sheathing  the  conduits  in 
the  leaves.  A  second  shell  is  formed  by  the  water-column  extending 
under  varying  tension  from  the  menisci  of  the  transpiring  cells  in  the 
leaves  downward  through  the  recently  formed  conduits  and  wood-cells 
to  the  root-hair  zones  in  the  roots  in  a  meshwork  more  or  less  complete. 
This  shell  occupies  2  or  3  layers  of  the  trunk  of  the  Monterey  pine, 
including  the  outermost  layers  of  the  terminal  parts  of  the  shoot¬ 
bearing  leaves.  In  the  older  central  part  of  the  stem,  the  tracheids 
contain  air  and  would  constitute  a  third  component  of  the  system. 

That  the  two  outer  shells  together  form  an  effective  enclosure  is 
proved  by  the  presence  of  gases  in  the  older  wood  at  pressures  gen¬ 
erally  much  lower  than  atmospheric,  and  with  a  composition  widely 
different  from  that  of  the  air.  The  most  prominent  feature  is  the 
increased  partial  pressure  of  the  carbon  dioxide,  600  times  that  of 
the  air  in  trunks  of  Juglans  in  the  autumnal  condition,  with  a  reduc¬ 
tion  of  the  oxygen  to  less  than  half  its  atmospheric  proportions. 

The  cambium  and  the  newly  formed  wood  are  subject  to  daily 
reversible  variations  in  thickness  which  are  associated  with  the  balance 
between  water  taken  in  by  the  roots  and  loss  from  the  leaves.  Man¬ 
ometers  connected  with  these  layers  by  tubes  filled  with  water 
show  an  increased  suction  under  any  set  of  conditions  which  would 
accelerate  water-loss. 

Recent  measurements  by  Ursprung  show  that  the  suction  force  of  the 
leaf-cells  which  constitute  the  upper  terminal  of  the  water  system  at 
mid-day  may  be  double  that  shown  in  the  morning.  The  graphs 
of  daily  variation  of  this  feature  of  Beilis  suggest  a  close  correlation 
with  variations  in  thickness  of  trunks  and  stems.  Suction  of  45 
atmospheres  was  found  in  leaves  of  Sempervivum  tectorum  and  in 
amounts  in  many  other  plants  which  would  furnish  ample  force  to 
move  the  column  of  water  in  stems  at  an  adequate  rate.1 

No  exudation  pressure  attributable  to  root  action  has  been  found 
in  the  pine.  Positive  pressures  in  bores  made  in  the  layers  carrying 
the  water-column  are  identifiable  with  the  flow  of  resinous  material 
from  the  canals  and  with  the  hydration-dehydration  curves  of  paren¬ 
chymatous  cells  in  a  cycle  which  come  to  an  end  within  3  days. 

Exudation  or  positive  pressure  has  been  found  in  the  massive 
cortex  of  cacti  which  is  due  entirely  to  the  hydration-distention  and 

1  Ursprung  A.  Einige  Resultate  der  neusten  Saugkraft  Studien.  Flora,  18-19,  566-599, 
1925. 


DISCUSSION. 


117 


subsequent  contraction  of  the  living  cells  contiguous  to  the  bore  holes 
and  hence  coming  quickly  to  an  end. 

These  results  are  in  agreement  with  the  conclusions  of  Molisch, 
that  exudation  pressures  are  due  to  the  action  of  cell-masses  contiguous 
to  cut  surfaces  or  bore-holes.1  Molisch,  however,  attributes  exuda¬ 
tion  to  traumatic  reactions,  or  rather  to  the  greater  osmotic  activity 
of  callus  or  wound  tissues,  an  interpretation  not  implied  in  my  con¬ 
clusions.  My  recently  described  experimental  studies  of  absorption¬ 
swelling  and  contraction  of  living  cell-masses  has  made  it  possible  to 
give  the  specific  explanation  outlined  in  the  preceding  paragraphs. 

The  fact  that  Molisch  observed  positive  pressures  as  high  as  0.98 
atmosphere  in  a  section  of  a  trunk  of  Juglans  regia  130  cm.  long  and 
12  cm.  in  diameter  is  fairly  conclusive  that  exudation  in  the  trunk 
can  not  be  referred  to  root-action.  This  does  not  impair  the  con¬ 
ception  of  the  endodermal  mechanism  cited  elsewhere  in  this  paper. 
Such  an  arrangement  may  be  necessary  to  the  production  of  pressures 
in  roots  as  reviewed  on  the  pages  that  follow. 

It  is  evident  that  exudation  might  be  produced  in  radial  bore-holes 
by  expansion  of  the  central  gas-body  in  the  trunk.  The  possible 
participation  of  living  cells  in  such  action  in  such  cases  is  not  to  be 
explained  by  wound-effects  as  proposed  by  Molisch  or  by  absorption 
and  dehydration  as  in  Carnegia.  Further  detailed  observations  will 
be  required  in  order  to  arrive  at  a  full  and  adequate  explanation  of 
“root-pressures,”  especially  as  manifested  in  stems. 

Some  suction  and  some  exudation  pressures  recorded  by  manome¬ 
ters  attached  to  bore-holes  or  to  stumps  may  be  attributed  to  the 
expansion  and  contraction  of  the  gases  included  in  the  central  cylin¬ 
der  of  older  wood.  The  water  introduced  into  a  bore  may  be  con¬ 
ducted  by  capillarity  for  a  distance  upward  and  downward  in  ves¬ 
sels  and  tracheids  determined  by  the  size  of  the  conduits,  resistance 
in  perforations,  and  pressure  of  the  gases  with  which  these  conduits 
were  filled.  No  bore-hole  has  been  made  in  any  tree  in  these  experi¬ 
ments  in  which  dye  was  not  conducted  downward  as  well  as  upward 
from  the  cavity.  The  sugar  maple  can  not  profitably  be  taken  as  an 
example  of  a  special  class  characterized  by  such  conduction  as  sug¬ 
gested  by  Priestley  and  Wormall.2  In  the  wood,  downward  con¬ 
duction  is  a  matter  of  the  keenest  interest  at  the  present  time,  and  it 
is  conceivable  that  when  an  upward  pull  is  exerted,  as  it  is  more  or 
less  constantly,  on  the  cohesive  meshwork  of  solution  in  the  wood 
that  it  would  tend  to  draw  liquids  into  the  region,  and  if  the  resis¬ 
tances  were  such  as  to  give  the  readiest  flow  downward  in  some  of 
these  tracts  a  mechanism  for  carrying  carbohydrates  to  the  roots 
would  be  furnished.  Ordinarily,  however,  experimental  results  can  not 

1  Molisch,  H.  Ueber  localen  Bliitungsdruck  und  seine  Ursachen.  Bot.  Ztg.,  60,  45-63,  1902. 

2  Priestley  and  Wormall.  On  the  solutes  exuded  by  root-pressure  from  vines.  The  New 
PhytoL,  24,  24-37,  1925. 


118 


HYDROSTATIC  SYSTEM  OF  TREES. 


be  so  interpreted.  Conduction  of  a  dye  or  other  reagent  from  a  bore 
both  upward  and  downward  may  be  simply  capillary  conduction  from 
a  bore,  mostly  determined  by  gas  pressures  less  than  atmospheric. 

The  failure  of  a  solution  to  move  downward  in  a  perforated  stem 
may  be  due  chiefly  to  the  fact  that  no  part  of  the  system  contains 
free  gases  or  gases  at  less  than  atmospheric  pressure. 

Previously  but  little  or  no  correlation  has  been  found  between  the 
pressures  registered  by  manometers  inserted  in  various  parts  of  a 
stem  or  trunk.  No  correlation  would  be  possible  unless  it  is  known 
what  regions  of  the  hydrostatic  system,  as  here  described,  were  tapped. 
Suction  and  pressure  are  determined  by  different  agencies  in  a  tan¬ 
gential  and  in  a  radial  bore,  and  by  combinations  of  the  two  groups 
in  stumps  of  branches,  stems  and  roots. 

It  is  obvious  that  a  manometer  attached  to  a  stump  will  connect 
not  only  with  the  inner  wood  containing  gases  and  the  sap-column 
under  tension,  but  also  with  the  cortical  layer  through  which  air  may 
pass.  In  actual  practice  when  rubber  pressure  tubing  is  clamped 
over  the  end  of  a  branch,  stem  or  root,  the  outermost  softer  layers 
are  crushed  so  that  the  cortex  is  sealed  off,  but  this  is  not  always  the 
case.  This  uncertainty  renders  it  difficult  to  interpret  results  which 
have  been  published  from  time  to  time,  since  it  is  not  possible  to 
identify  the  manometric  connections  established  in  the  experiments. 

The  pressures  at  the  cut  ends  of  roots  of  the  Monterey  pine  showed 
that  the  central  body  of  gas  was  continuous  in  these  organs  as  suction 
pressure  was  often  lessened  at  times  of  high  temperature,  dominating 
or  masking  the  pull  from  the  leaves  in  the  cohesive  column  of  water, 
extending  to  the  water  in  the  bore.  It  is  probable,  however,  that 
the  newer  wood  in  which  this  column  extends  is  partially  blocked  by 
resin  deposits  near  the  surface  of  the  cut  which  would  lessen  its  effect. 
The  action  of  resinous  material  was  seen  in  a  larger  root  where  it 
exuded  to  an  amount  creating  a  positive  pressure  for  a  brief  period. 

Unknown  disturbances  of  metabolism  doubtless  take  place  in  a 
separated  root.  The  initial  exudation  of  resin  may  be  held  to  account 
for  positive  pressures  shown  in  the  first  2  days  of  the  test.  That  a 
slight  positive  pressure  should  again  be  shown,  beginning  20  days 
later,  is  unexplainable,  except  in  so  far  as  it  may  be  connected  with 
the  inactivation  which  followed.  The  death  and  consequent  increased 
permeability  of  cells  surrounding  the  resin  canals  and  vessels  would 
furnish  material  for  such  exudation. 

The  results  of  the  tests  of  the  roots  of  Juglans  indicate  a  mechanism 
with  some  features  essentially  different.  Chief  among  these  is  that 
of  exudation  pressure,  recurring  through  long  periods,  at  the  end  of  a 
root  from  which  the  terminal  section  with  its  rootlets  had  been  re¬ 
moved.  The  lateral  branches  of  the  root  furnished  endodermal 
mechanisms  which  might  set  up  positive  pressures  in  the  parts  of 


DISCUSSION. 


119 


the  day  in  which  water-loss  by  the  leaves  was  least,  but  when  the 
transpiration  rate  was  highest  the  pull  in  the  water-column  equalized 
such  root-action  or  exceeded  it,  thus  setting  up  suction. 

Late  in  the  season,  however,  such  endodermal  action  must  be  taken 
to  have  ceased  with  growth.  It  was  seen  that  suction  diminished  in 
the  warmer  part  of  the  day  when  included  gases  would  show  the  high¬ 
est  expansion  and  pressure.  In  this  stage,  that  is  after  the  season 
of  growth  had  ended,  the  roots  of  the  pine  and  walnut  showed  suction 
variations  of  the  same  general  character.  The  differences  in  action 
were  manifested  during  the  season  of  growth. 

Separated  parts  of  pine  roots  showed  positive  pressures,  identi¬ 
fiable  with  exudation  of  resinous  material  from  canals  and  probably 
contraction  of  living  cells.  A  similar  preparation  of  the  walnut 
showed  exudation  of  a  type  in  which  endodermal  action  and  contrac¬ 
tion  of  living  cells  may  have  contributed.  Later  the  reaction  was 
that  of  a  shell  containing  gases,  suction  diminishing  in  the  mid-day 
period,  with  expansion  and  increased  pressure  of  the  gases  included. 
The  attachment  of  a  manometer  to  the  stump  or  branch  of  a  small 
pine  tree  connects  the  liquid  of  the  instrument  with  the  water-column 
as  well  as  with  the  “gas  chamber ”  of  the  interior.  Capillary  action 
and  variations  in  the  included  gases  determined  the  nature  of  the 
changes  in  all  such  cases. 

The  variations  in  Juglans  in  tests  in  which  both  the  water-column 
and  the  gas-chamber  were  connected  showed  some  noteworthy 
features.  A  short  stub  of  a  branch  in  which  presumably  the  gas- 
filled  center  connected  with  the  gas-body  in  the  trunk,  and  the  water- 
column  was  continuous  with  that  of  the  trunk,  showed  a  dominance 
of  positive  pressures  at  mid-day  early  in  the  season.  It  is  not  known  if 
expansion  of  gas  would  contribute  toward  such  results,  whether  or 
not  a  pressure  actually  in  excess  of  atmospheric  was  present.  It  is 
probable,  however,  that  the  so-called  “  root-pressure  ”  was  a  factor. 
After  a  mid-summer  season,  in  which  only  suction  was  observed, 
positive  pressures  were  again  noted  in  November,  not  only  in  the 
stub  but  also  in  the  radial  and  tangential  bores.  These  positive  pres¬ 
sures  were  at  mid-day  and  at  a  time  when  the  trunk  was  at  its  maxi¬ 
mum  temperature  for  the  day,  so  that  expansion  of  gases  was  doubtless 
an  important  contributory  agent. 

The  records  of  a  long  leafy  branch  showed  suction  only,  but  through¬ 
out  the  greater  part  of  the  season  a  mid-day  reduction  was  noticeable. 
The  water-loss  from  the  leaves  on  the  dozen  branchlets  was  at  all 
times  sufficient  to  balance  any  supply  by  “root-pressure/’  although 
the  suction  set  up  was  diminished  in  the  mid-day  period  at  the  time 
when  included  gases  would  be  at  their  highest  pressure. 

Exudation  pressures  were  a  marked  feature  in  the  tangential  bore 
in  the  height  of  the  growing  season  and  reached  a  maximum  early  in 


120 


HYDROSTATIC  SYSTEM  OF  TREES. 


the  morning  in  this  period,  decreasing  through  the  day  as  if  expressing 
a  balance  between  “root-pressure”  and  water-loss.  The  records 
bore  this  aspect  until  October,  at  which  time  a  lessening  of  suction  at 
mid-day  was  discernible  and  the  course  of  variations  was  similar  to 
that  in  the  radial  bore  and  in  the  branches.  The  accentuation  of  this 
condition  followed,  so  that  positive  mid-day  pressures  coincidental 
with  high  temperatures  of  the  trunk  were  seen  in  November. 

It  is  to  be  noted  that  Molisch  observed  a  morning  daily  maximum 
of  exudation  pressure  in  trunks  of  Juglans,  jEscuIus  and  Betula,  with 
a  diminution  at  mid-day,  indicating  that  these  records  were  made 
during  the  season  of  active  growth  and  that  the  bore-holes  were  cor¬ 
rected  with  the  ascending  water-column  under  tension. 

This  feature  of  positive  pressure  after  the  close  of  the  growing  season 
was  the  only  record  of  such  pressures  in  the  radial  bore.  Radial  bores 
connect  directly  with  the  central  gas-body  and  the  pressures  shown 
are  obviously  determined  by  changes  in  expansion  and  pressure  de¬ 
termined  by  the  temperature. 

The  difference  between  conditions  in  the  central  wood  filled  with 
gases  and  the  outer  wood  carrying  the  sap-column  under  tension  from 
leaf-action  is  well  illustrated  by  the  results  of  experiments  described. 
A  small  pine  tree  which  had  been  previously  bored  for  some  mano- 
metric  measurements  was  cut  down,  the  basal  section  including  the 
bores  removed  and  the  freshly  exposed  basal  surface  quickly  coated 
with  stiff  grease.  A  manometer  was  attached  to  a  bore  driven  upward 
from  this  surface  in  the  outer  sap-filled  wood  and  another  to  a  similar 
bore  in  the  older  gas-filled  wood.  Suction  in  the  last-named  instru¬ 
ment  rose  slowly  and  to  a  lower  maximum  than  in  the  instrument 
fixed  to  the  outer  wood,  in  which  a  continuous  tension  was  main¬ 
tained  by  pull  from  the  transpiring  leaves. 

In  fact  in  no  adequate  experiment  did  evidence  fail  to  appear  con¬ 
firmatory  of  the  conception  of  a  gas-filled  body  of  wood  and  outer, 
more  recently  formed  tracheids  and  vessels  in  which  a  water-column 
existed  under  tension.  The  two  regions  are  roughly  separable  in  the 
pine  where  the  sap-carrying  tracheids  contain  but  little  air,  and  in 
which  the  rate  of  conduction  is  comparatively  low.  In  dicotyledonous 
trees  large  vessels,  which  open  into  each  other  to  give  free  conduits 
of  great  length,  air  is  tapped  by  even  the  strictest  tangential  bores 
that  can  be  made.  It  is  notable,  however,  that  in  the  autumn  the 
outer  wood,  vessels  and  tracheids  of  dicotyledonous  trees  all  tend  to 
become  filled  with  water  according  to  Farmer.1  In  this  condition 
the  central  gaseous  cylinder  would  become  as  well  defined  as  in  the 
pines.  The  behavior  of  trees  of  the  two  types  show  suction,  indicating 

1  Farmer,  J.  B.  On  the  quantitative  differences  in  the  water-conductivity  of  the  wood  in 
trees  and  shrubs.  II:  The  deciduous  plants.  Proc.  Roy.  Society  B.,  90,  232. 


DISCUSSION. 


121 


a  similarity  of  relative  arrangements  of  gas  and  water  tracts  late  in 
the  season. 

The  widely  differing  and  partly  antagonistic  hydrostatic  features 
of  the  two  regions  are  so  arranged  as  to  render  of  no  practical  value 
the  results  of  a  great  number  of  experiments  in  which  pumps  and 
gages  are  affixed  to  stumps  of  stems,  branches  and  roots.  Suction 
and  pressures  taken  from  both  regions  are  the  resultant  of  a  number 
of  agencies,  the  effects  of  which  are  not  always  capable  of  ready  analy¬ 
sis.  This  view  is  based  upon  the  results  obtained  from  bores  made  in 
selected  layers  of  pine  trunks.  Suction  applied  to  the  ends  of  such 
stems  did  not  extract  sap  until  after  prolonged  treatment  and  after 
more  or  less  complete  displacement  of  the  air-body. 

Suction  of  about  half  an  atmosphere  drew  sap  copiously  from  the 
outer  layers  of  such  stems  in  a  few  seconds.  Dyes  applied  to  the 
surface  of  the  base  of  such  stems  move  4  to  15  cm.  per  hour,  while 
such  solutions  might  be  drawn  in  a  strictly  limited  tract  at  a  rate  over 
90  cm.  per  hour,  which  probably  represents  a  high  normal  rate  in  the 
intact  trunks  of  pine  trees. 

Such  experiments  serve  to  demonstrate  the  high  resistance  to  tan¬ 
gential  and  radial  conduction,  and  the  validity  of  the  conception  of 
a  cohesive  water-column.  It  is  evident,  moreover,  that  the  samples 
of  sap  obtained  in  this  manner  may  be  taken  to  be  nearly  identical 
in  composition  with  the  solutions  which  reach  the  leaves  in  normal 
standing  trees.  The  outermost  layer  of  the  pine  with  which  no  leaves 
are  connected  was  invariably  much  higher  in  sugar  (as  glucose)  than 
the  sap-carrying  layers.  The  solution  passing  upward  to  the  leaves 
in  the  second  and  third  layers  of  wood  carried  0.13  to  0.16  gram  per 
liter  in  June  when  the  outer  layer  had  a  0.27  gram  per  liter.  Con¬ 
centrations  in  both  regions  decrease  rapidly  when  cut  stems  are 
allowed  to  stand,  the  content  2  days  later  being  0.05  and  0.06  gram  in 
the  sap-carrying  wood  and  0.20  gram  in  the  outer  layer.  Sugars  are 
seen  to  accumulate  in  the  sap-carrying  wood  after  the  cessation  of 
growth  in  August.  A  detailed  series  of  analyses  would  probably 
show  greater  seasonal  variation  in  the  Monterey  pine  than  is  ascribed 
to  evergreens  by  Dixon  and  Atkins.1 

The  ascending  sap  stream  in  the  pine  would  contain  0.13  to  0.16 
gram  per  liter  glucose  and  also  be  highly  charged  with  C02,  as  the 
innermost  meshes  of  the  water-column  would  be  in  contact  with  a 
central  gas-body  in  which  the  partial  pressure  of  C02  is  about  200 
times  as  great  as  in  atmospheric  air.  Supplies  of  this  amount  might 
be  of  some  importance  in  the  photosynthetic  activity  of  the  leaf. 

The  meshwork  sap-column  of  a  composition  as  noted  passes  upward 
in  vessels  surrounded  by  sheaths  of  living  parenchymatous  cells, 

1  Dixon,  H.  H.,  and  W.  R.  Atkins.  On  the  composition  of  the  sap  in  the  conducting  tracts  of 
trees  at  different  levels  and  at  different  seasons  of  the  year.  Notes  from  the  Bot.  School,  Trinity 
Coll.  Dublin,  2,  No.  6,  p.  335,  1916. 


122 


HYDROSTATIC  SYSTEM  OF  TREES. 


which  usually  contain  more  starch  in  dicotyledonous  trees  than  in  the 
pines  or  through  the  tracheids  which  are  intimately  interwoven  with 
the  tall  flat  rays  comprising  tracheids  and  living  parenchyma. 

The  membranes  of  the  pits  between  the  two  kinds  of  elements 
constitute  actual  openings  through  which  plasmatic  strands  may  pass. 
These  strands  soon  disappear  in  maturing  wood  and  thus  make  pos¬ 
sible  the  continuous  cohesive  column  of  water  in  the  wood  of  the 
conifers,  in  which  movement  as  high  as  96  cm.  per  hour  has  been 
set  up  by  suction  less  than  an  atmosphere  as  noted  in  these  experi¬ 
ments.  A  much  higher  rate  would  seem  possible  in  the  wood  of  the 
oak  or  walnut. 

In  any  case  the  cohesive  column  may  be  visualized  as  filling  a 
capillary  tube  with  minute  lateral  openings  into  living  cells,  the 
colloidal  mass  of  which  is  highly  hydrated  in  a  solution  of  sugars  and 
salts  with  an  osmotic  value  of  several  atmospheres.  The  colloids 
extend  through  the  openings  into  the  wood-cells.  The  suction  power 
of  these  cells  would  absorb  water  to  a  point  where  it  would  be  limited 
by  the  permeability  of  the  plasma  and  stretched  tension  of  the  walls.1 

It  is  not  possible  to  make  exact  statement  of  the  condition  of  the 
plasmatic  strands  in  the  perforations  between  the  living  cells  and 
conducting  cells,  but  it  is  obvious  that  any  agency  which  would 
increase  their  permeability  would  allow  water  to  be  forced  into  the 
conduits,  setting  up  a  “  root-pressure  ”  in  the  water-column.  An 
alternation  of  such  action  would  furnish  the  pumping  action  upon 
which  a  pulsatory  theory  of  ascent  of  sap  has  been  based  (see  p.  195). 

It  is  not  clear  how  such  alternation  might  be  caused,  nor  has  any 
evidence  of  such  recurring  activity  been  uncovered  by  the  present 
experiments. 

It  has  been  found  that,  when  a  bore  cuts  the  outer  wood  of  a  conifer, 
first  water  is  drawn  into  tracheids  and  also  absorbed  to  the  limit  of  the 
suction  power  of  living  cells,  registering  suction  in  an  attached  man¬ 
ometer,  after  which  increased  permeability  and  escape  of  resinous 
material  under  pressure  in  ducts  and  canals  sets  up  a  positive  pressure, 
which,  however,  soon  comes  to  zero  and  the  cycle  is  not  repeated. 
Positive  or  exudation  pressures  may  also  be  caused  by  expansion 
in  the  central  gas-body,  as  has  already  been  described. 

While  the  observations  presented  were  begun  in  1924  and  carried 
intensively  through  7  months  of  1925,  the  discussion  of  certain  features 
is  reserved  until  the  records  are  continued  over  a  longer  period. 
The  value  of  such  extension  is  well  illustrated  by  the  work  of  Boehm2 
and  of  Molisch,3  both  of  whom  obtained  high  exudation  pressures  in 
dicotyledonous  trees,  in  tests  which  covered  more  than  one  season. 

1  Ursprung,  A.,  and  G.  Blum.  Eine  Methode  zur  Messung  des  Wand  und  Turgordruckes  der 
Zelle,  nebst  Anwendungen.  Jahrb.  f.  wiss.  Bot.,  63,  1-110,  1924. 

2  Boehm,  J.  Ueber  einen  eigenthiimlichen  Stammdruck.  Ber.  d.  deut.  Bot.  Ges.,  10, 539, 1892. 

3  Molisch,  H.  Ueber  localen  Bliitungsdruck  und  seine  Ursachen.  Bot.  Ztg.,  60,  45-63,  1902. 


SUMMARY. 


123 


SUMMARY. 

The  principal  results  of  the  work  described  in  the  present  paper 
are  as  follows: 

1 .  The  hydrostatic  system  of  tree-trunks  includes  a  central  cylinder 
of  old  wood  containing  gases,  a  layer  of  new  wood  carrying  the  cohesive 
column  of  water,  and  a  layer  of  living  cells  including  the  cambium. 

2.  The  layer  of  living  cells  is  impervious  to  gases  except  by  diffusion. 

3.  The  layer  of  recently  formed  wood  filled  with  water  is  also  imper¬ 
vious  to  a  radial  gas  flow.  The  living  rays  pass  through  this  region, 
the  inner  limits  of  which  are  not  well  defined. 

4.  The  gases  of  the  central  cylinder  in  Juglans  may  include  C02 
at  a  partial  pressure  600  times  as  great  as  in  the  atmosphere,  with 
oxygen  about  one-half  that  of  the  atmosphere.  Gases  in  the  cen¬ 
tral  cylinder  of  the  Monterey  pine  include  C02  at  a  pressure  200 
times  as  great  as  in  the  atmosphere,  with  oxygen  reduced  about  one- 
fourth.  These  disproportions  are  greatest  under  autumnal  conditions. 

5.  Pressures  in  the  central  gas-body  vary  chiefly  with  temperature. 
Gages  making  air  connections  register  pressures  only  slightly  less 
than  atmospheric  in  Queraus,  Pinus  and  Juglans. 

6.  Gages  connected  with  water-filled  cavities  may  register  suction 
as  great  as  0.5  atmospheres  in  which  capillary  entrance  of  water 
into  vessels  and  tracheids  is  concerned. 

7.  Suction  in  the  central  gas-body  is  least  at  mid-day  and  greatest 
at  daybreak  in  direct  opposition  to  the  course  of  water-loss  and 
contraction  of  recently  formed  wood  carrying  the  water-column. 

8.  Pressure  in  the  water-column  of  a  pine  tree  is  always  less  than 
atmospheric  in  bore-holes  after  2  or  3  days  and  the  suction  thus 
implied  is  greatest  at  the  time  of  the  highest  water-loss,  greatest 
contraction  of  the  wood  and  greatest  expansion  of  the  central  gas- 
body. 

9.  Positive  or  exudation  pressure  is  seen  in  a  pine  trunk  only 
during  the  first  2  days,  and  is  to  be  attributed  to  the  exudation  of 
resinous  material  and  contraction  of  living  cells.  Exudation  pressures 
as  high  as  4  atmospheres  have  been  recorded.  No  “root-pressures” 
have  been  found. 

10.  Positive  pressures  are  manifested  in  bore-holes  in  the  trunks  of 
Juglans  intermittently  for  many  months,  but  are  greatest  in  tangential 
bores  and  during  the  growing  season.  Positive  pressures  are  also 
found  in  bore-holes  penetrating  to  the  central  gas  body  after  growth 
has  ceased. 

11.  Exudation  pressures  are  shown  by  severed  roots  of  Juglans 
for  a  short  time  after  separation.  Exudation  pressures  over  extended 
periods  may  be  shown  by  the  cut  ends  of  roots  with  branchlets  which 
may  be  connected  with  the  action  of  these  laterals. 


124 


HYDROSTATIC  SYSTEM  OF  TREES. 


12.  Manometers  attached  to  stumps  of  stems  or  roots  by  enclosing 
pressure  tubing  register  a  resultant  of  the  action  of  capillarity  of 
liquid  used  in  making  the  connection,  the  variations  in  volume  of  the 
central  gas-body,  and  of  the  tension  in  the  cohesive  column  of  water 
in  the  wood.  In  some  instances  connection  is  made  with  outside 
air  through  the  cortex. 

13.  The  results  of  experiments  in  which  suction  or  pressure  is 
applied  to  the  entire  cross-section  of  a  large  stem  are  complicated 
and  not  easily  to  be  analyzed. 

14.  Suction  applied  to  an  entire  pure  trunk  is  not  followed  by  sap 
extraction  until  the  end  of  a  period  which  may  be  as  long  as  one  or 
two  hours. 

15.  Suction  of  0.5  to  0.24  atmosphere,  applied  to  water-carrying 
layers  of  Monterey  pine,  extracted  sap  within  a  few  seconds. 

16.  Suction  as  above  applied  to  an  entire  pine  trunk  caused  a  slight 
acceleration  of  the  rate  of  movement  of  fuchsin  in  the  water-carrying 
layers,  in  which  the  dye  usually  moves  4  to  15  cm.  per  hour. 

17.  Suction,  as  above  applied  to  newly  formed  wood  of  the  pine 
trunk,  caused  solutions  of  dye  to  move  at  rates  as  high  as  96  cm.  per 
hour.  It  is  assumed  that  a  sap  solution  would  be  carried  farther  in 
the  same  period. 

18.  Suction  applied  to  bore-holes  in  the  ends  of  trunks  caused  dye 
solutions  to  be  drawn  through  the  stem  in  limited  tracts  leading  to 
the  bores.  Manometer  tests  showed  but  little  effect  tangentially 
away  from  the  conduits  engaged. 

19.  The  sugar  (as  glucose)  content  of  sap  is  greater  in  the  outer 
layers  than  in  the  inner  layers  carrying  the  sap-column  of  the  pine. 
The  proportion  of  sugar  present  is  high  in  the  spring,  is  reduced  during 
the  growing  season  and  increases  after  wood  formation  has  ceased. 

20.  Upwardly  moving  columns  of  water  in  the  Monterey  pine 
occupy  the  layers  connected  with  the  leaves.  The  wood  of  the 
terminal  internode  and  of  the  second,  third  and  fourth  layers  of  older 
nodes  are  so  connected.  The  nature  of  the  movement  in  the  outer¬ 
most  layer  of  wood  was  not  determined. 

21.  The  downward  movement  of  solutions  from  a  bore  in  a  trunk 
was  seen  in  the  pine,  walnut  and  oak.  Such  a  movement  is  not 
a  special  characteristic  of  the  maple.  The  action  in  question  seemed 
to  be  due  to  capillarity. 

22.  Positive  or  exudation  pressures  in  the  cortex  of  the  tree-cactus 
are  due  to  absorption  of  water  and  subsequent  contraction  by  living 
cell-masses.  Such  action  may  also  occur  in  Pinus,  but  the  principal 
factor  in  this  tree  is  the  discharge  of  the  resin-canals.  The  duration 
of  positive  pressure  in  both  cases  is  limited  to  the  first  few  days  after 
a  bore  hole  is  made. 


SUMMARY. 


125 


23.  Exudation  pressures  in  Juglans,  attributable  to  the  action  of 
living  cells  and  with  a  maximum  at  dawn  and  minimum  at  mid-day, 
occurs  in  the  new  wood  of  Juglans  and  has  been  observed  by  Molisch 
in  sections  of  trunk  standing  in  water.  These  pressures  are  therefore 
not  to  be  connected  with  “root-pressure.” 

24.  Positive  pressures  in  bore-holes  and  stubs  of  branches  after  the 
cessation  of  growth  are  coincidental  with  temperature  expansion  of 
the  central  gas-body  in  Juglans.  Such  pressures  reach  a  maximum  at 
mid-day  and  a  minimum  in  the  morning,  or  at  the  time  of  lowest 
temperature. 

25.  No  positive  or  exudation  pressures  in  the  trunks  of  Carnegiea , 
Pinus,  Juglans  or  Quercus  have  been  observed  which  can  be  posi¬ 
tively  connected  with  osmotic  pressures  set  up  in  the  root-systems. 
Exudation  pressures  in  roots  of  Juglans  which  have  been  recorded 
may  be  due  to  osmotic  action  of  the  endodermal  mechanism.  The 
existence  of  such  a  connection  remains  to  be  established. 


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UNIVERSITY  OF  ILLINOIS-URBANA 

581.11M14H  C001 

THE  HYDROSTATIC  SYSTEM  OF  TREESSWASHINGT 


3  0112  009922490 


